As Paul can no doubt attest, in years gone by, all telephone connections at the exchange were hand soldered, individually
For sure. You could see a main or intermediate distribution frame with literally
thousands of soldered terminals, both for the fixed lines and for the jumpers.
One of the tasks set for early-stage apprentices was to wire up a large multi-pair cable on to a terminal block on a dummy board, correctly identifying the pairs by color code and putting them on the block in the correct sequence, soldering all connections properly, and then neatly lacing the wiring.
