PURPOSE: To allow telephone and telegraphic exchange operation with one set of switch, by making sampling through clocks in synchronizing with transmission bit of time division multiplex PCM telephone signals for telegraphic signals and transmitting them with specific channel.

CONSTITUTION: From a time division multiplex PCM telephone terminal station 1, a time division multiplex PCM telephone signal and a control signal are applied to a telegraphic multiplex terminal station 2. At the terminal station 2, a telegraphic signal is sampled with the clock in synchronizing with transmission bit of the time division multiplex PCM telephone signal and transmitted to a transmission line 3 via the specific channel of the time division multiplex PCM telephone signal. Further, at a multiplex telegraphic separation and synbthesis terminal station 4, a transmitted signal is converted into a time division multiplex telegraphic signal having the same timing as the time division multiplex PCM telephone signal. Further, at a time division exchange switch 5, the time division mutiplex PCM telephone signal and the time division multiplex telegraphic signal are exchanged.