PURPOSE: To arbitrarily select various PCM (pulse code modulation) in accordance with the condition of a signal by storing PCM different in contents in plural storage means and arbitrarily using them by switching.

CONSTITUTION: Contents of encoding different from one another are stored in plural storage means 16, 18, and 20, and the storage means 16, 18, or 20 to which the digital signal from a comparing means 12 should be supplied is selected to easily change contents of encoding to which the digital signal supplied as the address signal of these storage means is subjected. Since plural storage means 16, 18, and 20 are provided, contents of encoding in one storage means can be changed even in the middle of encoding in another storage means. Thus, contents of PCM are changed on demand.