b. Both the transmitter and the receiver have the same number of operating modes. The selected mode
determines the number of voice-frequency channels that can be used, the maximum baseband frequency range
that can be satisfactorily processed, and the type of modulation that will be employed. An example of a nine-
mode system is shown in table II.
c. Mode selection in the receiver involves the selection of appropriate filters, deemphasis circuits, output
circuits, and feedback circuits. The selected filters and circuits control the bandwidth of the receiver, which, in
turn, controls the number of channels that can be passed on to the terminal equipment.
d. Additional controls throughout the voice-frequency circuits are used to control the range of the
baseband frequencies. Compandor assemblies contain compressors and expandors, compressors for voice-
frequency signals being transmitted, and expandors for signals being received. These circuits compress the
dynamic range of the voice-frequency signals at the sending end, and expand the signals to their original
condition at the receiving end.