| 摘要 |
A telecommunication system of the kind having a telephone handset connected to an exchange via a line incorporates a beacon (22) in the line for receiving a question signal from test equipment associated with the exchange and for sending an answer signal to the test equipment. The beacon (22) senses voltages in the two wires making up the line but is otherwise isolated from the line via a diode bridge (20) and a protection circuit (21) and high value resistor Rp. Previously known beacons were connected directly into the line to sense current and thus could not be protected by high value resistors.
|
