128 132 are set to make the translated low frequency components in the output signal on the order of 12 to 15 db below the level of the high frequency components converter 122 serves to convert the high frequency components of speech signals from a microphone 133 to the low frequency band for transmission in that band with the low frequency components this converter includes a volume compression and a g c circuit 134 a 1600 hz high pass filter 136 a summation network 137 a balanced modulator 138 and a 1400 hz low pass output filter 139 the gains of filters 136 139 are set to make the translated high frequency components of the output signal on the order of 12 15 db below the level of the low frequency components injection signals for modulators 131 138 are provided by a common 1500 hz oscillator 144 the outputs of filters 132 139 are connected to the inputs of a summation amplifier 142 and the output of this amplifier is connected to an output terminal 143 for delivery to the transmission line or other voice processing circuitry deconverters 123 124 process the signals transmitted in the high and low frequency bands respectively and utilize a common input terminal 146 and a common a g c circuit 147 at the output of the a g c.