Mollison ISC

Mollison ISC
	Ericsson ARM20 crossbar (TXK5) called Mollison, there were also models of both at the training centre. The ARM 20 was the largest in the world and consisted of four separate switches. Two were used for incoming traffic and two for outgoing. These were know as Twin A and Twin B in each unit and each twin could access ports on its' twin via interconnecting links. The Route Marker (RM) on one twin knew if there was available circuits on the other. Photos: Mollison ARM20 (Bob Outtram 1989)
\| Mollison ISC (TXK5) \| The IATAE \| The IMC \| Peter Walker recalls \|
Mollison ISC TXK5 Bob Outtram who managed the unit for many years recalls... "Pictured is the Ericsson ARM20 crossbar(TXK5) called Mollison, there were also models of both at the training centre. The ARM 20 was the largest in the world and consisted of four separate switches. Two were used for incoming traffic and two for outgoing. These were know as Twin A and Twin B in each unit and each twin could access ports on its' twin via interconnecting links. The Route Marker (RM) on one twin knew if there was available circuits on the other. This was the first time BT had contracted a non-British core switch, however, the contract was with Thorn Ericsson's which was 51% Thorn and consequently had the governments blessing. Ericsson's British venture started there!" The IATAE (International Accounting and Traffic Analysis Equipment) At Mollison the equipment only processed international call accounting information. And although it did NOT monitor traffic or process fault information, it was still (perhaps incorrectly) referred to as an IATAE.
	The International Accounting and Traffic Analysis Equipment (IATAE) Mollison IATAE (UAC1610) 32 bit processor 64Mb RAM!
	The International Accounting and Traffic Analysis Equipment (IATAE) Mollison IATAE (UAC1610)
The IMC (International Maintenance Centre) ISMC - International Switching Maintenance Centre for TXK5s Centralograph Equipment for print outs of call failures. Service Equipment Alarm for monitoring forced release of equipments. Traffic and Statistical Meters for analysis. Electronic Traffic Recorder (MET2 at Mollison ISC)
	Mollison International Maintenance Centre (IMC)

	ISMC Had an Electronic Traffic Recorder (MET2). This was later replaced by an OMT.

ITMC - International Transmission Maintenance Centre for TXK5s Supervisory Console. Test - Jack Frame. Test Consoles. Access Selector. Exchange Tester - trolley and rack mounted kit.
	The portable exchange testers: These trolleys were designed to negotiate the narrow aisles behind the racks and to plug into a 80 way highway which was multiplexed around the exchange. Their use was as an artificial traffic generator.

Peter Walker recalls...

The Mollison TXK5 had an entirely different atmosphere to the De Havilland TXK2 exchanges. The relay sets were in metal cans, similar in a way to Strowger technology, while the switches had glass at the front of their covers. The Route Markers and Markers were all centralised in suites, so this area of the exchange was very noisy in the busy hour. You could tell from the sound that a Route Marker made whether the call had been successfully switched across the exchange. I got very familiar with the portable Exchange Testers while doing the System Appraisal tests at Mollison. So that we could work uninterrupted by the continuing commissioning work, these tests were done overnight. We did find a few design faults which Ericsson rectified of course, though most design issues had been sorted much earlier through Ericsson providing a test model of TXK5 (without any switches) in the circuit lab in Armour House in 1973. I arranged for circuits to be brought in from every conceivable kind of exchange type to prove interworking. During these tests, I even found some flaws in the design of Strowger GSC equipment which would have made them vulnerable to the "phone freaks".

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