PURPOSE: To attain flexibility and expanding performance of a PCM format by using a read only memory element for format control.

CONSTITUTION: The information which word in words 0∼m in the PCM format is to be used as a sub commutation data is written in addresses 0∼m of a ROM9 and the said information is read as a signal (f) outputted sequentially from a word counter 7. An address control section 10 generates an address data (p) designating an address of a ROM11 based on signals f, h, j. The information of an input channel designation address (q) of a multiplexer 12 is written in a ROM11. All telemetory data (r) inputted to the multiplexer 12 are switched sequentially by the address (q) according to the PCM format and outputted as a PCM telemetory signal (d).