The Teleco negative impedance repeater CNQ 523 have been designed as terminal or intermediary amplifier for telephone connections at two wires, in the range 300-3400 Hz. Particularly for the urban areas (subscriber’s connections, among local exchanges or between local exchange and intercity exchange) on carrier constituted by pupinized and not pupinized cables, overhead lines.

All the signallings of direct and alternating current pass through the CNQ 523 amplifier, as well as the power supply current. The amplifier allows the operation of the telephone circuit also in case of missed power supply of the same amplifier.

A series amplifier, a parallel amplifier, the interconnections between the two amplifiers and the power supply circuit essentially constitute the CNQ 523. The gain and the equalization are regulated by an artificial network also on pupinized cable.