Telephone side tone arrangement

A telephone set performs a side tone network selection test under control of the telephone's microprocessor 7, by switching into the transmission circuit in turn each of a plurality of side tone networks, Z1 to Z4, applying a test signal from a signal generator 8 with each side tone network, measuring the side tone level produced by each side tone network in a measuring circuit 9, storing the measured results in RAM and comparing the results to identify the network which produced the optimum side tone level, and selecting this network as the side tone network for the telephone.