An amplifier combining the properties of high gain, wide band audio response with input signal conditioning, constant current output for use on two wire systems and compound negative feedback for resistance to oscillation in acoustic feedback environments. The direct coupled amplifie
A dual timing circuit for use with a subscriber's telephone circuit operated in response to two manual switch operations to simulate the placement of the subscriber's phone in the "on-hook" condition for two different predetermined periods of time. One "on-hook" period being for the
An amplifier for use with an electret microphone utilized as a telephone transmitter in a hand held telephone unit or handset. Incorporated into the circuitry is a band pass filter which substantially inhibits feedback "singing" which occurs because of reflection when the handset or tele
