Automatic measurement of telephone microphone current - involves insertion of jumper cable to connect milli-ammeter in series

摘要

The current in the microphone of a telephone handset is measured automatically without the need for dismantling the handset to make the necessary connections. This is effected by use of a jumper cable. A telephone handset which includes a microphone has a plug to permit connection to the telephone network. A jumper cable which plugs into the handset connector has the microphone wire connected in series with a milliampere meter while the other three wires are directly connected to a moulded connector and to the telephone network. This enables the milliampere meter to indicate instantaneous current in the microphone circuit.