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When the first automatic exchange was introduced at Holborn in London in the mid 1920s there was an immediate problem of connecting callers to all the surrounding manual exchanges. This was first done by connecting the caller to the operator at the called manual so that the caller could ask her for the number wanted and she could connect him to the multiple.(See Slide four of Images above) As automatics grew in number , better ways of completing this type of call were adopted and in the 1930s in large networks the Coded Call Indicator (CCI) working was introduced. With this system CCI equipment was fitted at the calling auto exchanges that was able to record and store the digits dialled by the caller and then wait until the call could be accepted by the manual exchange. At the called manual special CCI B positions each with 36 connecting cords, were fitted with a display panel in the operators keyshelf.
When an operator became free the calling auto could send the number in the form of light and heavy current codes and bring up the number on the operators display panel. She could then connect the call to the multiple or send back engaged code as the case may be. There was no need for the operator to enter the call and it was very fast operating, hence the large number of cords, but when it was overloaded it caused problems because the calls queued up back at the auto causing floor alarms to alert the engineer to the problem. During the war this could easily happen immediately after an air raid or VI or V2 incident when hundreds of callers would call to see if their friends and relatives were O.K. and this was very common
After the war early in 1947 I was an engineer at Palmers Green exchange in north London when a floor alarm indicated that there was trouble on the CCI equipment. On investigation , I found it was due to delay on calls to the nearby Tudor manual exchange at Muswell Hill., a few miles away. I called the manual and asked to speak to the Testing Telephonist (TT) who had the job of dealing with service enquiries. When I asked if they were busy she light heartedly replied that “she” wasn’t ! As you can imagine, one thing led to another and we arranged to meet outside a sweetshop in Muswell Hill. I said I would wear a multicolour scarf so she would know me , and she has always laughed because it turned out to be a sombre woollen tartan scarf that I wore because of the terrible weather of that winter. I recall we went to the pictures at the local A.B.C. cinema and so started our long friendship with marriage the following year. Today over sixty four years later with 2 children , seven grandchildren and four great grandchildren, we always have a chuckle when young people talk about blind dates and think what our family owes to the complications of Coded Call Indicator working!
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