Blog Archives

Keymile UMUX – Multiservice access solutions

Comprehensive Functionality

The UMUX platform provides carrier-grade reliable multi-service multiplexing and aggregation functions over copper and fibre networks. A variety of voice (POTS, FSX, FSO, ISDN) and data (e.g. G.703, V.11, V,24, V,35) interfaces, SHDSL and Ethernet (including PoE+ and EoS) services are available. 

The modular and flexible housing provided by the UMUX 1500 (8U, 21-slot) and UMUX 1200 (4U, 8-slot) 19” subracks provide the perfect solution for all applications and locations, offering redundant controller and power supplies.

‘Legacy’ telecoms history

The UMUX SDH product portfolio was originally launched 1991 by Ascom, which subsequently became Keymile.

In 2003, by when 70,000 units had been deployed worldwide, the ‘enhanced’ UMUX multiservice access platform was introduced, offering the delivery of ATM, TDM and IP based services from the same platform, with support for IP/Ethernet, ADSL, VoDSL and G.SHDL.

Keymile was sold to ABB in 2017 when the UMUX range was discontinued, and then was acquired in 2019 by DZS. 

Continuing to provide operational service

The UMUX, together with the UNEM network management system and ‘sister’ LINERUNNER and MILEGATE products, continues to provide operational service with various global Operator, Utilities and Transport companies. 

@YellowsBestLtd supports requirements to maintain these networks by supplying various spare part items from refurbished and surplus stocks in perfect working order.  

There follows a list of the main elements that are typically provided, though other items can be provided. Please let us know of any specific requirements you may have. We look forward to being of assistance.

Part CodeUnit typeDescription
A31A1679U1500-CSU1500 Core R2 (DC) for 19″ mounting (incl. Subrack, POSUM, COBUX 128x2Mb/s XC)
A30A0205DATAS-FUData Interface unit.  Multi-Interface V.35, V.24/V.28, X.24/V.11, RS485, Ethernet, 4 ports, all options
A24A3323LOMIF-FU2 Mb/s IF (E1), 8 x G.703 Interfaces
A24A3651COBUX-FUControl Unit Standard,128x2Mb/s XC
A21A2865EXLAN342POTS FxO Interface Unit, 12 ports, complex impedance
A31A7871GECOD371Data IF 64kb/s G.703 codir., 8 interfaces
A24A3338LOMI4-FU2 Mb/s IF (E1), 4 x G.703 Interfaces
A24A7979POSUM306Power supply unit -48VDC 85W
A30A1442SUBH3-FUPOTS FxS  Interface Unit, 30 ports
A31A7873SULIS393ISDN Interface Unit Subscriber side, ISDN BA 2B1Q, 8 interfaces
A23A9927SYNAC-FUSDH Access bridging unit SBUS-PBUS, 8xVC-12; no external IF
A24A1989TUPON-FUOptical Trunk Interface 8Mbit/s 1xopt.(o), 4xel.(e), 1550nm, PBUS access

Posted in News, Solutions Tagged with: , , , , , , , , , , ,
Blog Archives

Launch of Telecoms Products

Management Services and Solutions

@YellowsBestLtd provides professional Management Services for Business Development activities and Enterprise Support of Infrastructure. We source Solutions for Sustainable Systems maintenance.

Together with our broad range of new and ‘legacy’ equipment Technologies, we have now launched a portfolio of telecoms Products, enabling Customers to do more whilst reaping cost-benefits. 

Below is listed the Market Sectors of our Customers, together with the equipment Technologies and telecoms Products we can supply.

We’re always keen to expand our portfolio, so please let us know anything you require as we can usually provide whatever is needed.

Market Sectors

  • Maintenance Companies
  • Private Networks & SMEs
  • Public Safety (Police, Fire, Ambulance)
  • Systems Integrators
  • Telecoms (Carriers, Operators)
  • Transport (Rail, Metros, Underground, Highways, Aerospace)
  • Utilities (Electricity, Gas, Oil, Water)

Equipment Technologies

  • Optical Fibre and Copper, PDH Access & SDH Transmission, Telecommunications equipment
  • TDMoIP, Pseudo-wire, IP Data and Voice Telephony
  • Carrier Ethernet, C / DWDM optical fiber multiplexing technology
  • Microwave Radio, wireless coverage solutions
  • Private Mobile Radio (PMR), TETRA infrastructure, terminals, accessories
  • CCTV Cameras, security systems
  • LED displays and information signs
  • Antennas and Radio Direction Finding (RDF)
  • Solar Energy off-grid installations
  • Power supplies and peripheral devices
  • IT network, workstation, server, storage products
  • Network Management Systems (NMS), OSS software
  • Test Equipment

Telecoms Products

  • Telephone Lines & Calls
  • Connectivity Voice & Data
  • Hosted Cloud Telephony
  • Telephone Payment Line
  • PBX
  • Call Centre solutions
  • Dialler Service
  • Reports & Statistics
  • Cost Centre Billing
  • Conference Calls
  • 03 & 08 Numbers
  • Voice and Omni Hub
  • Marketing & Inbound numbers
  • VOIP & IP PBX / Cloud Telephony
  • ADSL & Internet connections
  • SMS Text messaging & survey
  • Fax and other servcies
Posted in News, Solutions
Blog Archives

Nokia ‘Dynanet’ Telecoms – Stock disposal

‘Last chance’ for spares!

The Nokia ‘Dynanet’ family of PDH Transmission telecoms products has served customers well for the last 20+ years, and indeed some networks continue providing good operational service. 

Dynanet Subtrack

@YellowsBestLtd has supported requirements to maintain these networks by supplying various spare part items from refurbished and surplus stocks in perfectly working order.

However, demand has recently reduced and warehouse space is needed, so now the time has come to recycle / dispose of a large proportion of the remaining equipment. Consequently, there remains a short-term opportunity to obtain any items still required to maintain existing deployed infrastructure, before the products are gone.

Here is a stock list of the main items currently available, though there may be a few additional parts that can be supplied. Hence, please check and if you do have any requirements, please let us know – before it’s too late! We look forward to hearing from you.

Part  NumberDescription
24204TPSO H/W Module
CC 24002DB2 Branching Unit, B2 2×2 Mb/s 75 ohm
CC 24011DB2 2 Mb/s Switching Unit, X2 75 ohm
CC 24101DN2 Interface Unit (IU2) 2×2 Mb/s 75 ohm
CC 24111DN2 Control Unit (CU) 75 ohm
CF 24186DN2 19″ Subrack
CF 24186.09DN2 Subrack 19″, grey-L91 EMC
CG 24170DN2 Bus Power Unit (BPU)
CG 24171Extended DN2 Bus Power Unit (EBPU)
CU 24013Data Interface Unit (DIU) 2M, nx64k: G.703/704, 75 ohm
T30506.0917-slot DYNANET Subrack
T30851.02Subrack Power Adapter (SPA)
T37870.01NDM ACM2 19in 17-slot subrack
T37871.01NDM DN2 19″ 17-Slot Subrack
T37882.01NDM DC Unit (NDUe)
T37882.02NDM DC Unit (NDUe)
T37885.01NDM Ring Generator
T37889.01NDM Backup Unit (NBU)
T65520.01ACL2 RM DC Power Gen
T65580.01ACL2i PF GEN Line Terminal Card
TA 21513Optical Line Terminal Repeater 2-8 M, 1300 nm LED MM/SM
TA 21516Optical Line Terminal Repeater 2-8 M, 1300 nm LASER SM
TC 21101DM34 Mux Card
TC 21301DM8 Multiplex Equipment, 75 ohm
TC 21705Supervisory Substation
TC 21710.01TMS Adapter
TG 21261Ring Generator 25HZ 15W
TU 21122.5Data Interface Unit (DIU) 48..64k V.11 10ch
TU 21124Data Interface Unit (DIU) NX64k V.11/V.35/X.21 2CH
TU 21124.05Data Interface Unit (DIU)
TU 21125Data Interface Unit (DIU) 48..64k with sync, X.21
TU 21205Channel Unit SUB/SUB
TU 21206Channel Unit SUB/SUB
TU 21215Channel Unit SUB/EXCH
TU 21216Channel Unit SUB/EXCH
TU 21234.20Channel Unit E&M/VF-P, 10 CH, 20 E&M CH
TU 21236.10Channel Unit (CU) 8ch E&M/uP: 2xe&m/vf
TU 21255.01Channel Switch, 4 PORT
TV 21640.08Power Interface Adapter DC
Posted in News, Solutions Tagged with: , , , , , , , , , , , , , , ,
Blog Archives

Legacy Computing – Windows through time

DOS Beginnings – the early days of ‘personal computing’

The ‘Personal Computer’ (PC) launched by IBM in 1981 was a breakthrough that revolutionised the workplace, though the early ones were quite limited especially in terms of how to use them and what they displayed. Not only did they have no ‘touch screens’ for ‘swiping’ and ‘apps’ as we know them now, but there was no ‘graphical user interface’ either. Rather than a ‘desktop’ with icons and a mouse pointer, there was just a black screen with text and a flashing cursor.



This was Microsoft DOS (Disk Operating System), which seemed to be the ‘proper’ way to use computers for at least a decade.

GEM - Atari ST

GEM – Atari ST

Indeed, some PC users were initially ‘suspicious’ of icons and windows which had appeared on the Apple Mac as well as other alternatives in use like GEM on the Atari ST.

People had become so used to typing commands, and knew all the ‘switches’ and other modifiers e.g. DIR /W to display a list of the files across the screen rather than in a column. And ‘WP’ was all you needed to get ‘Word Perfect’ to launch – the then favoured Word Processor, which gave rise to some still familiar short-cuts like ‘Control-C’ to copy.

Desktop computing takes-off and ‘Windows’ takes-over

Windows 3.1

Windows 3.1

Windows 3.1 showed PC users something different from around 1992, when 386 and 486 PCs powerful enough to run it well became available.

mouse tutorial

mouse tutorial

It even came with a tutorial to show users how to use a mouse!

Windows 3.1 floppy disks

Windows 3.1 floppy disks

No-one enjoyed having to install it using 7 floppy disks though.

And at first it seemed somewhat unnecessary to run existing applications.


Windows 95 – DOS prompt

Indeed, there was a bit of an ‘outcry’  that Windows 95 and later variants didn’t first boot into DOS!

But then it was realised there were some key benefits. Now you could delete a whole directory in one go without having to clear out each ‘level’ – not always the safest feature! Email really became more useable when you didn’t have to log in specifically to check to see if you had messages; now it could be running all the time in its own window.

The rise of the Internet – and security issues


Windows 98 ‘desktop’

With each variant of ‘Windows’ came more sophistication, and suddenly a whole world of connected information could be accessed with Netscape and then Internet Explorer, which then meant Windows really became a ‘must have’.

Internet Explorer - WinXP

Internet Explorer – Windows XP

Certain difficulties were experienced getting old and new applications to behave themselves in the Windows environment; stability and also backwards compatibility started to become issues. Users now had to deal with ‘blue screen’ crashes of Windows, and then a variety of increasing security threats and viruses requiring ever-more enhanced anti-malware protection applications and mandatory backups.

The continuing need for ‘Legacy’ support

Although the majority of modern offices, educational establishments and homes now use the latest PC hardware as well as phone and tablet computing devices running the newest generation of operating software and applications, some industrial workplaces have professional implementations of systems that still make use of early computing platforms (ranging from desktop PCs to OSS servers), where the basic requirements are unchanged, and particularly in stand-alone use where security threats aren’t an issue. And some people still have old PC games to play!

Drive Setup

Drive Setup

It can however be quite a task to restore the operation of legacy systems, particularly if backups are missing or incomplete.

FDISK for partitioning

FDISK for partitioning

Associated issues include obtaining the appropriate hardware replacement parts such as disks (modern versions can be too high capacity to work well with old systems) requiring the right settings of cylinders, heads and sectors, and preparation using FDISK and FORMAT commands.

Floppy Disk

Floppy Disk

Software ‘patching’ of configurations may be needed, hunting out correct versions of driver files and specifying the right parameters. Creating a floppy disk with ‘boot’ files can also be a helpful tool!

Emulation and Virtualisation

There’s still a way today to run legacy software even without the old PC hardware, and that’s via the ‘joy’ of emulation and virtualisation. Even using an Apple Mac or Linux computer, it’s possible to run various flavours of Windows legacy software.

Particularly useful applications to enable this include:



DOSBox – a handy emulator tool which enables the running of old DOS based applications in an application window. Relatively straight-forward to setup, with the ability to ‘mount’ folders so that files can be imported.



VirtualBox – a fully featured virtualisation tool that allows the creation of ‘virtual machines’ into which can be installed a full operating system, such as Windows 3.1, Windows 95 or Windows XP. The tool also emulates CD and Floppy drives for  loading disk images and running legacy applications.

CPU fix for Win95

CPU fix for Win95

Takes a bit of work to set up, preparing a virtual ‘hard disk’, and then installing the operating system. There’s a ‘work-around’ needed to take account of modern processors being ‘too fast’ for the old operating software! Also, to set the display to the necessary resolution and get sound working, special video and audio drivers may need to be installed.




Or you could try the Windows 95 ‘computer as an’ App created by Felix Rieseberg, which can be downloaded and installed on macOS, Windows and Linux!


@YellowsBestLtd we can assist with support services for both legacy and new software and hardware solutions, so please get in touch if you have any requirements you’d like to discuss;  we look forward to hearing from you.

Posted in News, Services, Solutions
Blog Archives

Nokia, Marconi and Ericsson SDH – ‘Synfonet’, ‘SMA’ and ‘OMS’

‘Legacy’ Networks; long history, but still important and operational!

Back in the day, when PDH (Plesiochronous Digital Hierarchy) was all there was for telecommunications optical and copper transmission, a familiar site was the ‘Multiplexer Mountain’.


PDH Multiplexer Mountain

Then came the new transport technologies: SDH (Synchoronous Digital Hierarchy) for high-speed digital communication (via optical fibre and radio links); and (D)WDM ((Dense) Wave Division Multiplexing) as an optical solution for raising the capacity of existing fibre networks (particularly when the fibre-count was limited).

Nokia launched the ‘Synfonet’ range as the big brother to their successful ‘Dynanet’ PDH portfolio, with SDH capacity of initially STM-1 (155MBit/s) and STM-4. Later came STM-16 and WDM.

Synfonet – STM-1/4

  • All in one subrack (REG, TM, ADM, DXC)
  • Wide range of tributaries
  • 64kbit/s cross-connection server
  • Upgradable from STM-1 to STM-4 while in service
  • Compact, flexible and easy to expand


Nokia Synfonet

Synfonet – STM-16

  • 2.5 Gbit/s, four times the throughput rate of STM-1/4


Nokia Synfonet

Synfonet – WDM

  • 4–channel multiplexing / demultiplexing
  • 8-channel multiplexing / demultiplexing
  • Up to 20 Gbit/s per fibre


Nokia Synfonet

But in 1999, Marconi Communications acquired (for over $100M) Nokia’s Synfonet brand, SDH and DWDM transport equipment products and about 120 staff from its Cambridge research and development business under the deal.

Inevitably over time Marconi rationalised their portfolio and the Synfonet range was discontinued, in favour of the SMA and MSH SDH equipment.

Business however took a downward path and in 2005 Ericsson acquired the key assets of Marconi (for SEK 16.8 billion). “Marconi” then became the registered trade-mark branding for Ericsson to promote these products, until phasing them out.

Marconi® Series 1 SMA1 Multiplexer

  • Flexible SDH Multiplexer
  • Terminal, Add/drop (ADM) or Digital Cross-Connect (DXC)



Marconi® Series 3 & 4 SMA Multiplexers

  • Full range of options, including size and power variants
  • SMA1, SMA4, SMA16c and SMA16c+ Series 3 models
  • Tributary interfaces from 2MBit/s to STM-4
  • SMA1/4, SMA1/4c, SMA1/4E and SMA1/4UC Series 4 models
  • Supports ATM and IP with enhanced data functionality
  • Metro access and metro core deployment, and customer premises



Marconi® SMA 16-64 Multiplexers

  • Advanced ADM, DXC and low-order aggregator
  • Delivers 2.5GBit/s and 10GBit/s data transport capabilities
  • Full VC-12 granularity allowing single-layer access without VC-4 layer
  • Metro core deployment



Marconi® MSH Series

  • Family of STM Multiplexers, Regenerators and Cross Connects
  • MSH11C, MSH41C, MSH51C, MSH63, MSH64, MSH64C and MSH86 Models.



Marconi® MSH2K

  • Foundation of Marconi’s switching portfolio
  • DXC functionality, capacity of 320GBit/s
  • Support for STM-1 to STM-64 electrical interfaces
  • Embedded DWDM and support of SDH protection / restoration
  • Seamless transition from Ring to Mesh network architectures
  • Capable of upgrade to Multi-Layer Switch (MLS)
  • Metro core deployment



Marconi® MSH64C

  • Based on same platform as MSH2K
  • Core ADM/XC, 80GBit/s switch, capacity of 32 x STM-64 interfaces
  • Consolidating and grooming traffic.
  • Gigabit Ethernet interfaces for data transport
  • Embedded DWDM interfaces



From 2007, Ericsson launched the (still) Marconi® branded OMS (Optical Multi Service) portfolio of advanced SDH multiplexers, including OMS 1200, OMS 1400 and OMS 1600 providing multi-service products for Metro-Edge and Metro networks. The “Marconi” brand was later dropped by Ericsson for this OMS range.

OMS 1200 range

  • Range of SDH ADM
  • Optimised for ring and terminal applications


OMS1200 series

OMS 1400 range

  • Compact energy efficient multiservice and packet optical transport.
  • Optimized for use in Metro Access networks
  • Carrier class Ethernet and TDM services interworking with metro and core Networks based on SDH, Ethernet or IP/MPLS
  • Applications ranging from high capacity customer sites, fixed or mobile backhaul/Radio Access Network (RAN) aggregation and transport



OMS 1600 range

  • Compact, multiservice transport and switching platform
  • Terminal, Add/Drop and Cross-connect multiplexers
  • Line, ring, star and meshed networks
  • Modular configurability, comprehensive switching options
  • High port density reducing space and power consumption
  • Range of data and TDM services, fulfilling ITU- T G.782 requirements


OMS1600 Series

The OMS range provided packet evolution capabilities to Ericsson’s optical networking portfolio and strengthened its Full Service Broadband offering, meeting the demand from operators to evolve their network to support a mix of services and traffic types, with dexterous backhaul connectivity, TDM or Ethernet-based, with telecom quality, flexibility and scalability.

Perhaps this ‘potted history’ helps explain the ’journey’ these products took, and clarifies why they can be referred to as both Nokia and Marconi, or indeed Ericsson. Although now discontinued by these manufacturers, the products are extensively deployed and still in use by Telecoms Operators, Utilities and Transport companies.

Supporting ‘Legacy’ Networks and Keeping Customers Operational

From time-to-time Customers benefit from services from @YellowsBestLtd

  • Locating Nokia, Marconi, Ericsson (and other vendors) hard-to-find replacement items
  • Hardware repair services to existing parts
  • Supplying additional spares for newer systems to increase capacity or provide alternative interfaces

This way these ‘legacy’ but still important networks can continue to be maintained and kept operational.

To illustrate the possible requirements for spares and repairs, some key parts from the above networking technologies are listed, as follows:

Nokia - Synfonet


Part Code Family Description
STM-4 (T30023.01 – 71.02) Synfonet STM-4 card
STM-16 (T30172.02 – .06) Synfonet 2 x STM-1/4 WDM Mux
WDM MUX (T30172.41) Synfonet 2 x STM-1/4 WDM Mux
STM-1 E/140M (T3033.01) Synfonet 140Mbit/s STM-1 electrical IU
34M/45M (T30046.02) Synfonet 34/45Mbit/s electrical IU
2M TA (T30041.01 – 43.01) Synfonet 2Mbit/s interface units
CU (T30073.01) Synfonet Node control and timing unit
SSW (T30053.01) Synfonet System Switch Unit
SU-A (T30084.01) Synfonet Service unit / EOW
SPIU (T30093) Synfonet PSU Card
TSW0 (T30110.01) Synfonet 64 kbit/s cross-connect unit
TSW1 (T30063.01) Synfonet Cross-connect unit for STM-4

Marconi - SMA / MSH


Part Code Family Description
02HAM00002AAJ SMA-1/4 21 X 2M LTU Balanced
02HAM00003AAL SMA-1/4 63 X 2M LTU Unbalanced
03HAT00010AAS SMA-1/4 10/100MB Ethernet Module
1HAM61217AAK SMA-1/4 Power Unit
1HAT 60796 AKU SMA-16 STM-16 OPT.TCM AHK S16.1 (SC)
1HAK 60596 AAE SMA-16 STM-16 RX OPT S16.1
1HAK 60701 ABM SMA-16 STM-16 TX OIC 1310nm (FC/PC)
1HAT 60730 ADL SMA-16 STM-16 LINE UNIT 1550nm (FC/PC)
1HAT 60730 AJX SMA-16 STM-16 LINE UNIT 1310nm (FC/PC)
1HAT 60730 AMA SMA-16 STM-16 L-16.1 SC
1HAT 60730 ANS SMA-16 STM-16 L-16.2/3 SC
SN99AD SMA-16 Power Supply Unit
Part Code Family Description
133-1467/01 MSH86 Matrix Shelf
131-9475/21 MSH64 STM-64 S64.2 SC/PC
131-9475/22 MSH64 STM-64 L/V/U64.2 SC/PC
131-8685/01 MSH11C 3 X 34MBit/s Tributary Unit G.703
133-1260/01 MSH84 MSH86 Shelf Type 5
130-3118/01 MSH84 Trib Matrix Board
130-3132/01 MSH84 Control Matrix Sub Unit
130-3142/01 MSH84 Main Control Sub Unit
1MBD60697AAT MSH2K Shelf
02MBB00001ABG MSH2K S-16.1 Module, LC
02MBB00001ACY MSH2K L-16.1 Module, LC
02MBB00001ADR MSH2K L-16.2 Module, LC

Ericsson – OMS


Part Code Family Description
03HAG00001AAX OMS1200 A/D Mux System Chassis
03HAM0019AAQ OMS1200 HI Power DC Supply
03HAN00007AAH OMS1200 AC Power & Battery Backup
03HAN00009AAM OMS1200 Fan Unit
03HAT00041AAQ OMS1200 Common Control ADM Unit-A
03HAT00041ABH OMS1200 Common Control ADM Unit-B
03HAT00045ABR OMS1200 Ethernet Prnt Card
1HAT61107ABC OMS1200 64 x 2M Core Trib Card
1HBA60828AAX OMS1200 32x 2M Unbalanced LTU
1HBA60832AAA OMS1200 32x 2M Balanced LTU
1HAT61106BAE OMS1200 Comm/Aux/ANC Unit
1HAM61217ABC OMS1200 Power LTU Mod
Part Code Family Description
03HA500032AAC OMS1664 STM-1 Switch Card
03HAM00006AAT OMS1664 STM-1 Line Terminating Card
03HAM00015AAG OMS1664 10/100 Electrical LTU-Type 2 (SK57BC)
03HAT00015AAD OMS1664 STM-4 Line Card
03HAT00016AAF OMS1664 STM-4/16 Core Card
03HAT00021AAK OMS1664 STM-16 Line Card
03HAT00020AAH OMS1664 STM-64 Line Card
03HAT00029ACM OMS1664 16xE1
03HAT00053AAK OMS1664 140M Transmux Card
03HAT00057ABL OMS1664 Ethernet L2 Data Switch Prnt Card
03HAT00054AAM OMS1664 Ethernet Layer 2 (8+16 Ports) (SK58AB)
1HAG60619AAK OMS1664 Standard Shelf
1HAG60620AAF OMS1664 Compact Shelf

Please get in touch and let us know what you need to keep your network in good shape!

Posted in News, Solutions
Blog Archives

“TESTERS” – Test Equipment to suit all deployed technologies

Customers who own infrastructure systems usually require some form of test equipment to assist with the build, operation and maintenance activities.

Given the mixture of old and new technologies now deployed, consequently the range of available test equipment options has grown considerably. And like the infrastructure systems themselves, new functionality demands and obsolescence issues also affect the associated test equipment needs and availability.

@YellowsBestLtd assists Customers by sourcing the required test equipment, supplying either modern or legacy units. Often refurbished ex-hire equipment in excellent condition and at commercially attractive prices makes sense over leasing. This ensures the continued availability of sets of the appropriate specification, which may become discontinued by the manufacturers over time.

If necessary, we can also arrange the repair of existing units, especially those that perform very specific functions that cannot easily be replicated with more recent equipment.

There follows a brief description of many of the types of test equipment available; we would be very keen to hear from you to understand your specific requirements, so please get in touch!

Calibration Checkboxes

Calibration checkboxes, or electrical checkboxes, are used for routine observations of test equipment and allow users to maintain accuracy in between official calibration procedures. Suitable for use with PAT testers and with other testers and instruments.

Calibration Checkbox

Calibration Checkbox

Component Analysers

These test the efficiency and status of components including transistors and capacitors. An essential instrument for development engineering when specific components are used in product design.

Component Analyser

Component Analyser

Earth Loop Testers

Loop impedance testers, or loop testers, verify the loop impedance of a live electrical circuit without disconnecting from the electrical supply. Most testers include non-tripping RCD technology as standard to prevent unexpected outages.

Earth Loop Tester

Earth Loop Tester

Earth Testers

These verify that electrical current paths are safely earthed. Earth spike testers, high current loop testers with earth stakes and leads are available.

Earth Tester

Earth Tester

EMF Meters

EMF meters are used for verifying the presence of electrical magnetic fields given off by electrical equipment. Ideal for use in heavy-duty electrical applications and laboratory testing conditions.

EMF Meter

EMF Meter

EVSE Testers

EVSE testers are purpose-built for the installation, testing and maintenance of electrical vehicle supply equipment and are an essential for use by electrical vehicle charging point installers, manufacturers and anyone else involved with EVSE equipment.

EVSE Tester

EVSE Tester

Insulation & Continuity Testers

A wide range of insulation and continuity testing instruments which include Megger insulation testers, insulation resistance testers, Fluke testers and insulation meters from Amprobe, DiLog, Seaward, Metrel, Martindale, Kewtech and Extech.

Insulation and Continuity Tester

Insulation and Continuity Tester

LCR Meters

LCR meters get their name from their testing capabilities – they can test inductance (L), capacitance (C) and resistance (R).

LCR Meter

LCR Meter

Multifunction Testers

Ideal for use when completing or testing an electrical installation. The huge range of MFTs include the Fluke 1600 range and Megger installation testers.

Multifunction Tester

Multifunction Tester

Optical Fibre Inspectors

Quickly find and inspect the right port. Like having a built in flash-light so you can see in dark areas and dense panels. Pause button holds the image for viewing when it’s hard to get it just right. Bright backlit display. Screw-on probe tips to support most connector types.

Optial Fibre Inspectors

Optial Fibre Inspectors

Optical Fibre Visual Fault Locators

Locates fibres, finds faults, verifies continuity and polarity. Locates visual faults including tight bends, breaks and bad connectors. Easily verifies polarity and identifies fibres. Features continuous and flashing modes.

Optical Fibre Visual Fault Locator

Optical Fibre Visual Fault Locator

Optical Power Meters

Multimode and Singlemode Power and Loss Measurements. Multiple kit configurations with light sources for single mode, multimode and PON fibre optics. Min/Max capability automates tracking of intermittent power fluctuations.

Optical Power Meter

Optical Power Meter

PAT Testers

For Portable Appliance Testing (PAT) routine safety checking of electrical equipment, including dual insulation test voltages and portable RCD lead testing, with adjustable PASS testing limits and substitute/mains powered leakage testing procedures.

PAT Tester

PAT Tester

Power Quality Analysers

These provide a comprehensive snapshot of how power is being used in your facility and verify where energy is being lost. The latest power analysers and power analysis tools include those from Fluke and Hioki.

Power Quality Analyser

Power Quality Analyser

Production Line Safety Testers

Perfect for laboratories and product design applications, the equipment in this category can be used to verify electrical safety, service equipment using multiple electrical parameters and to simulate PAT conditions.

Production Line Safety Tester

Production Line Safety Tester

Proving Units

An essential accompaniment to a voltage tester, proving units verify that the tester remains accurate both before and after testing. Both the NICEIC and NAPIT strongly recommend using these regularly when testing.

Proving Unit

Proving Unit

RCD Testers

For testing RCD trip time and overall residual current device safety/efficiency. Available are handheld RCD testers, Megger RCD testers, RCD analysers and multifunctional RCD testers which also measure loop and PSC.

RCD Tester

RCD Tester

Socket Testers

These testers are placed into a socket to assess faults with the wiring using audio/visual feedback.

Socket Tester

Socket Tester

Telecom Datacom Analysers

Ideally suiting traditional telecommunications networking requirements, typically providing testing at V.24, V.35, V.11/X.21 interfaces at rates up to 2 Mb/s.  Also a full range of BER/BLER measurements, control-circuit timing analysis with transitions diagrams and storage in text and graphic form.

Telecom Datacom Tester

Telecom Datacom Tester

Voltage Testers

Voltage Testers

These verify the presence of voltage, and allow full test of voltage levels. Instruments are available from the leading test equipment manufacturers such as Fluke, Kewtech, Martindale, Amprobe and Megger.

Voltage Tester

Voltage Tester

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Data Centre Solutions – Keeping IT cool!

In order to get the best out of data centre infrastructure, ensuring equipment runs at its most efficient, reducing risk of failure and extending its life span, attention should be paid to ensuring the optimum operating environment. Efficiencies impacting on both the building cooling systems and power for room hardware (servers, switches, routers, etc.) means that improvements will pay for themselves, whilst also lowering the carbon footprint to the benefit of all. Solutions range from quick deployment for office computer room spaces with low power demands through to high density Data Centre applications delivering true containment giving scalability, mixed power zones and zero hot spots.

@YellowsBestLtd we would be very keen to discuss further; since the exact project requirements dictate the costs and savings to be gained, we can arrange a site survey as appropriate without cost or commitment. Hence please contact us; we look forward to hearing from you.


Ultrasonic Humidifiers

Low energy ultrasonic humidifiers have been widely used in data centre projects for many years. They consume a fraction of the energy of an equivalent steam humidifier, providing an assistance to data centre cooling with hygienic operation and virtually maintenance-free operation. There are a range of units available for installation within air handling units, cooling corridors or in the data hall itself, on any scale.


Cold Aisle Containment

Cold Aisle Containment is a non-intrusive bespoke retrofit to data centres, whereby the cold aisle is contained and supply and exhaust air separated to maximise cooling efficiency. By creating a positive pressure, air is directed straight into the servers, making them run more efficiently, whilst preventing recirculation of air back to the computer room significantly improves the efficiency of the building’s cooling system. Better control of the room’s temperature results in energy savings, and providing temperature equilibrium across all servers addresses the problem of overheating in the top third of the rack, where traditionally most server failures occur.

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Legacy and New Infrastructure Spares

Most Customers’ infrastructure systems now consist of a wide range of technologies from the very old to relatively recent, having been built to serve operational requirements for a number of years. In many cases, these requirements don’t significantly change, and it therefore makes sense to keep these systems in place to maximise the use of the investment and avoid whole-scale change-outs that would be costly, disruptive and unnecessary.

@YellowsBestLtd locates hard-to-find replacement spare parts to keep legacy infrastructure in operational service that has been deemed ‘obsolete’ by the manufacturers, as well as supplying additional spares for newer systems that can be used to increase capacity or provide alternative interfaces.

Typically we provide refurbished spares, tested and working, but often it is the case that unused products from surplus stocks can be supplied. Hence for both old and new systems, we are usually able to source parts at very commercially competitive rates and with short lead-times.

Here is a selection of items that we’ve recently been helping customers procure or obtain parts for. Keen to hear what requirements you may have, so please get in touch.

Alcatel AnyMedia Access System
Bosch MIC-400, -550 and -7130 Cameras
Dialogic I-Gate 4000 System
Huawei UMG8900 Node
Marconi ST68NB Matrix and 1HAT60558ADV
Meraki MS250 switch and MR52 access point
Motorola Terayon DM6400 Network CherryPicker
Nokia Dynanet PDH Subrack and 9500 MPR ODU
Pelco S5220 Spectra CCTV Camera
Siemens SRT1 C Base Band Unit
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Professional CCTV Cameras

In response to a strong demand for a diverse range of Professional CCTV cameras, we are providing both new and refurbished ‘legacy’ models from a number of manufacturers, to suit our clients’ exact requirements.

Industrial and professional use dictates key features such as a robust weather-proof housing, excellent optical quality, Pan Tilt & Zoom (PTZ) with high magnification, plus options including wiper (for clearing the lens), heater (for extended operating temperature range) and privacy masking. To support existing deployed networks, matching the communication protocol is critical, as well as the appropriate video standard (e.g. PAL).

There follows descriptions of some of the cameras YellowsBest has recently sourced and supplied to our customers, however, we are always keen to receive further enquiries and seek to provide alternatives as necessary; please contact us to discuss your requirements.


Bosch MIC series PTZ cameras

The MIC Series are best-fit cameras for high quality surveillance security applications, installed into the harshest of environments, thanks to its IP68 rating. This tough and vandal-resistant casing provides protection from the elements and physical attack. An integrated, long life silicone wiper, and a reversible rain shield ensure high quality images regardless of the installed environment.

The brushless-motor technology offers ultra-reliable operation with full 360º continuous rotation pan and 186º tilt control for exceptional viewing capability. Small increment pan speeds from just 0.2º per second to 120º per second gives the user precise control. This speed control is especially important when used with video analytic systems, particularly for tracking subjects when fully zoomed in. The MIC Series cameras are simple to integrate and use within systems that already use Bosch AutoDome cameras.

Typical of the range of products meeting professional needs, Bosch cameras have been available for a considerable time, and whilst continuing to fulfil the same basic requirements, have undergone a number of changes over the years in the portfolio which are important to understand. In particular, Bosch previously acquired the range of cameras from ‘Forward Vision’, and consequently it is critical when sourcing additional units to match the communication protocol in use i.e. FV, Pelco or Bosch. The main models (ranging from previously produced and currently available) include:

  • MIC-300 Series
  • MIC-400 Series
  • MIC-500 Series
  • MIC-550 Series
  • MIC-612 Series
  • MIC-7000 Series
  • MIC-9000i Series

There are also two product families, the ‘Classic’ standard camera and the more advanced ‘Professional’ series.

Therefore it is worth analysing the structure of the full model number in detail to ensure all requirements are met:



MIC – Metal (IP68 weather proof housing)

500 – Camera series (e.g. 300, 400, 440, 500, 550)

AL – Case Style (AL = Aluminium, STS = Stainless Steel, IR = Infrared LEDs included)

B – Colour (i.e. Black, Grey, White)

U – Configuration (C = Cantered, U= Upright)

R – Protocol (W = Forward Vision, P = Bosch, D = Pelco P/D, R = multi-protocol (S/W selectable))

1 – Wiper (1 = Wiper fitted, 2 = No Wiper)

4 – Heater (3 = Heater fitted, 4 = No Heater)

6 – Privacy masking (5 = Privacy fitted, 6 = No Privacy)

18 – Optical Zoom (18x, 28x, 36x etc)

P – Video standard (i.e. PAL, NTSC)

Not all options were available for all camera types, and the above model numbering applies to the ‘Classic’ series products. For the ‘Professional’ series, the ‘UR136’ part of the above number is omitted, since these models are by default Upright, multi-protocol units with the Wiper, Heater & Privacy functions included. Hence the part number is shorter, e.g. MIC-500-AL-B-18-P.


360 Vision Technology ‘Predator’ cameras

Since its inception in 2002, 360 Vision Technology has developed an extensive range of analogue, high definition IP, white light, infrared, cooled and uncooled thermal, polished stainless steel and radar controlled CCTV surveillance cameras to suit a broad range of general and harsh environment applications across many market sectors.

The Predator is a high performance, fully featured range of ruggedised PTZ Cameras designed and manufactured in the UK. The Predator range comes with multiple protocols as standard allowing quick and simple integration with many leading DVR’s, matrices and IP VMS systems. The Predator range covers all applications with a comprehensive range of models including analogue, HD, Thermal, Radar, and Stainless Steel versions. Predator cameras can be supplied in any colour, in any quantity.

Key features:

  • NEW Sony Starvis Modules – Ultra low light performance
  • ONVIF 2.4 Profile S Fully Compliant
  • Full Web Server Set Up
  • 1080p Full HD 2MP
  • 30x and 20x Optical Zoom options
  • Ultra Low Light options (0.1Lux colour)
  • ANPR compatible
  • Privacy zones as standard
  • High Light Suppression to eliminate glare from vehicle headlights and other bright objects
  • High quality accurate motors
  • Colour / mono, Analogue and IP camera options
  • Triple Slip Ring technology for preset accuracy and smooth movement
  • Rain Guard around the optical glass to reduce water on the screen
  • IR option for 400m illumination
  • Dual IR & White Light LED Option for 250m (IR) 250m (White Light)
  • Wiper option with programmable wipe settings
  • Washer option
  • Inverted or upright mount
  • Easy & quick setup software
  • UK supported and supplied
  • Colour at Night™ Technology for true colour at night
  • Unique alarm activated White Light illumination for enhanced CCTV Surveillance
  • Any colour Paint & Finish options
  • Marine Paint Preparation with 10 Year Paint Guarantee



Ganz ZC-YX/NX270 Series – 700 TVL Digital Day/Night  cameras

These high performance camera features Ganz GX5 technology, combining 700TVL, WDR (wide dynamic range), intelligent image enhancement and advanced OSD controls. These highly sensitive cameras are designed to deliver an unprecedented level of resolution, sensitivity and control for optimal video surveillance in all conditions.

Key features:

  • 700 TVL Super High Resolution
  • Extremely High Sensitivity Day/Night mode 0.07 lux (colour), 0.007 lux (B/W)
  • Super Low Light Performance 0.00015 lux (Sens up, 512x mode)
  • Automatically switches between 4 pre-programmed profiles for best image results
  • Smart Day/Night mode synchronizes with IR LED
  • 2D/3D Digital Noise Reduction
  • Test Pattern Output with colour bar
  • 12VDC or 24VAC Operation, Auto-Sensing
  • UL Listed
  • A time saving Pro-Pak kit is available for outdoor installations, including camera and a selection of Day/Night compatible varifocal lenses pre-installed in a rugged outdoor housing
  • True WDR, Digital Day/Night and True WDR, True Day/Night models also available.
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Nokia ‘Dynanet’ – Still Operating, Still in Demand!

Nokia ‘Dynanet’ PDH Telecommunications Product Portfolio

Still Operating, and Still in Demand!

We’re pleased to have recently helped Customers locate additional spares of this incredibly reliable and therefore popular telecommunications infrastructure equipment.

The range was originally produced by Nokia, and has been extensively deployed and in operational service around the world for over 20 years. It has formed the backbone of PDH and Access networks for many Customers across the Telecom Operator, Utilities and Transportation market sectors.

Recent Requirements

We’ve recently supplied Customers with these spare parts:

  • Smart Branching Unit (TU 21743)
  • DC/DC converter -24..-48V / -48V,-60V (21263)

These represent popular choices, but see below for an extended list of other immediately available items.

Future Dependability

It makes sense for Customers to use these spares as replacements as well as to add additional capacity to their existing networks, given the faultless performance of the products, rather than undertake costly and time-consuming wholesale replacements, given that in many case their basic telecommunications  requirements have not  changed.

Plus the ‘Dynanet’ product range has proven itself to be dependable over an extended period. How many of the latest products will be available in 5 or 10 years’ time, let alone in over 20 years?

Dynanet – an overview

 Nokia DYNANET is a family of multiplex, branching, cross-connect and line equipment.

The DM2 equipment has been designed for multiplexing analogue speech and signalling as well as data channels of different bit rates into a common 2 Mbit/s frame. The dynamic branching equipment DB2 and the cross-connect equipment DN2 increase the flexibility and application range in the DYNANET family.

The DYNACARD data channel unit selection covers the bit rates from 0.3 kbit/s up to 1984 kbit/s compliant with the V- or X-series of the ITU-T Recommendations. Other DYNACARD channel units provide specialised interfacing functions for Voice and Data applications.

The heart of the equipment is a MUX unit which is common to all channel and special units of the DM2 system. The MUX unit communicates through a 2 Mbit/s internal bus with the tributary units and carries out the 2048 kbit/s framing according to ITU-T G.732 standard.

The common MUX unit also inserts the signalling information into time slot 16 or provides the time slot 16 as a 64 kbit/s data interface, e.g., for use with a separate signalling equipment.

Analogue and digital services are realised with interface-specific channel units that connect to the DYNACARD bus. The channel units contain from one to ten voice channels, depending on the complexity of the interface.

Each individual voice or data channel can use any 64 kbit/s time slot, several time slots or only part of the capacity of one time slot. The allocation of time slots to different voice/data channels is independent of physical unit placement.

The DYNACARD VF channel unit selection provides analogue interface with signalling adaptation ranging from subscriber signalling to various types of junction line signalling. The signalling can be either channel associated or common channel signalling. In subscriber applications subscriber line testing is also available.

Immediately available from Refurbished Stock

Here is a list of items currently available from refurbished stock. All in excellent working condition, and can be delivered in a matter of days. No long lead time! But do remember that many items may be in short supply, so worth acting now and purchasing any spares you might need to avoid future disappointment!

Part Number Description
24204 TPSO H/W Module
CC 24002 DB2 Branching Unit, B2 2×2 Mb/s 75 ohm
CC 24011 DB2 2 Mb/s Switching Unit, X2 75 ohm
CC 24111 DN2 Control Unit (CU) 75 ohm
CF 24186.09 DN2 Subrack 19″, grey-L91 EMC
CG 24170 DN2 Bus Power Unit (BPU)
CU 24013 Data Interface Unit (DIU) 2M, nx64k: G.703/704, 75 ohm
CU 24101 DN2 Interface Unit (IU2) 2×2 Mb/s 75 ohm
T30506.09 17-slot DYNANET Subrack
T30851.02 Subrack Power Adapter (SPA)
T37870.01 NDM 19in 17-slot subrack
T37882.01 NDM DC Unit (NDUe)
T37889.01 NDM Backup Unit (NBU)
T65580.01 ACL2i PF GEN Line Terminal Card
TA 21513 Optical Line Terminal Repeater 2-8 M, 1300 nm LED MM/SM
TA 21516 Optical Line Terminal Repeater 2-8 M, 1300 nm LASER SM
TC 21301 DM8 Multiplex Equipment, 75 ohm
TC 21710.01 TMS Adapter
TF 21090.09 Subrack 19″, (EMC), grey
TU 21122.5 Data Interface Unit (DIU) 48..64k V.11 10ch
TU 21125 Data Interface Unit (DIU) 48..64k with sync, X.21
TU 21236.10 Channel Unit (CU) 8ch E&M/uP: 2xe&m/vf

This represents a list of the most common elements Customers need, but please do contact us if there’s something specific you’d like us to seek out for you. Always happy to help!

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