Continued from: Jobs I've Had - Telecom Australia (5) After completing the training in Sydney it was back to Sherwood EMG to begin a period of preforming maintenance work on the equipment I had spent months learning about, combined with connecting new telephone services, connecting special services for banks etc., and fault finding on these as well. This was the most enjoyable period of my 22 years with Telecom Australia. The telephone exchange equipment, known as an ARE-11 exchange, was fascinating to work on. Any time on any day I could be chasing obscure faults which could be physical wiring faults, worn out or poorly adjusted electro-mechanical relays, software faults in the processors which controlled the exchange, or hardware faults with the electronic components or circuit boards. The image above shows one suite of equipment, made up of multiple racks, and each rack could have multiple crossbar switches (glass covers), or multiple relay sets (grey metal covers). There is also a front and rear side to each rack. This is a subscriber stage which connected 1000 phone lines to others phone lines either within the same exchange or to junction circuits to other exchanges. If the exchange had 7000 phone lines connected to it there would be seven of these suites. In addition to that there were suites dedicated to incoming circuits from other exchanges, outgoing circuits to other exchanges, group switching stages, the processor control equipment, electronic interface equipment to link the processors with the relay-based technology, and more. As the image below shows with multiple suites needed for all the equipment, these telephone exchanges were quite big, and usually full of equipment. At the end of each suite of equipment there were coloured lights to show the status of the equipment in that suite. Red indicated a fault requiring urgent attention, yellow was a less urgent fault to attend to and white indicated some equipment was manually blocked out of service. There were also alarm bells for various urgent faults.
I hope these images build a picture of just how complex an ARE-11 (processor controlled crossbar) telephone exchange was. Literally thousands of relays, thousands of metres of cabling, hundreds of circuit boards and more... Despite this complexity I found it easy to locate faults when they occurred. I used to joke that a 'good technician' used all his senses when fault finding. You could listen to the exchange switching a call and hear at what point the call failed (generally speaking); you could see a badly adjusted relay when you removed the grey metal cover; you could smell a burnt out component like a resistor or capacitor; you could feel with your fingers a relay that was sticky and slow to operate. The only sense I could not incorporate was taste..!!
There were supplies of most spare parts at each exchange, sometimes you would have to travel to another exchange to find the right part, and failing that you would have to drive to the city and visit Hesketh House in Elizabeth Street where a larger pool of spare parts was held. We had to manage our own supplies of spare parts and re-order items when stock became low. Faulty circuit boards were sent away for repair and replaced with new items.
Faults occurred any time day or night and we were called out when required at night or on the weekend to attend to faults that could not wait, or that could not be remotely managed by the Brisbane After Hours Centre. Much of the exchange equipment was duplicated so that if a fault developed the suspect equipment could be blocked out to prevent telephone calls failing. Other times when exchange equipment failed it was a case of find the fault and fix it as soon as possible as every failed telephone call was a loss of revenue - that was when the pressure was on. I am pleased to say I always succeeded and it was satisfying quickly analyse the situation, change a part, then listen to the click of the relays and know by the sound alone that everything was returning to normal. Every now and then I would be at an exchange and the normal click of the relays would suddenly increase to a chaotic rate. This happened when radio stations had a quiz, or when concert tickets went on sale. There was a specific number range allocated to this (223 0xxx) and the telephone network was designed to handle this sudden surge in telephone calls without impacting regular phone calls. The problem was that some businesses just advertised regular phone numbers and with many hundreds or thousands of simultaneous calls to the same destination the entire exchange and telephone network would be thrown into massive congestion. My only regret was that this type of equipment was later phased out in preference to fully digital equipment which required far less maintenance. There was a strange fault that existed at Jamboree Heights in the 376 1xxx group prior to it being upgraded to digital, something that caused a massive but short-lived chatter of relays, but did not effect phone calls. I was somewhat progressed in identifying the cause when the equipment was decommissioned and changed over to digital. I never got to solve that mysterious fault - and I still think about it to this day..!!
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AuthorI love to understand things, how they work, why they happen - I'm always learning and keen to investigate... Archives
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