Five-line single cord switchboard, unknown maker, British, 1900-1909.
This telephone switchboard would have been used in small offices, where only a few telephone lines were needed. Each line terminates in a socket, called a 'jack', on the panel, and in a plug at the end of a cord. The sixth plug and jack are part of the operator's telephone circuit. To connect two subscribers the operator inserted the plug of the required subscriber's line into the jack of the caller's line.