sentences:  In order to get the transmitter to key reliably, sometimes the continuous tone that holds the transmitter on may have to be set so it is heard in the transmit audio.Sometimes equalization problems with a telephone circuit make it necessary to run higher levels than a circuit with a flat response from 300 to 3000 Hz would require.Normally a phone circuit ordered as a PLPA or conditioned type results in a 300 to 3400 Hz response which easily handles all tones used in a tone remote radio system.