In the early days of telephony, calls were connected manually by a switchboard operator .
The next stage of development saw the introduction of automatic telephone exchanges which dispensed with the need for human intervention.
A local telephone exchange establishes connections between the subscribers of a local network. In this case, an analogue electrical signal is switched via electromechanical components. If the first digit dialled by the subscriber is a zero, he or she is put through to the trunk or long-distance exchange.
The electromechanical system exhibited here was in use in Hagen-Eilpe until 1994, when it was replaced by a digital switching system. Photo: Jan Braun, HNF