PURPOSE: To transmit speech between a command issuer and a determinate receiver to plural command receivers by providing an adder to add the voice of the command issuer and that of the determinate receiver and the command receiver.

CONSTITUTION: At the initial state of a voice simultaneous command, a speech path 10 for command issuing and a speech path 8 for command reception are formed, and a speech path for determinate receiver is not formed i.e. the command issuer 1 is connected to the input of the adder 7, and the output of the adder 7 is connected to the command receivers 2 and 3 in plural, and the command receivers 2 and 3 can listen to the voice of the command issuer 1. When the command receiver 2 is set as the determinate receiver by the operation of the command issuer 1 or 2, the output of the command issuer 1 is connected to the input of the adder 7 and that of the determinate receiver 2, and the output of the determinate receiver 2 is connected to the input on the other side of the adder 7 and that of the command issuer 1, and the output of the adder 7 is connected to the command receiver 3 in plural. Mutual speech between the command issuer 1 and the determinate receiver 2 can be performed, and the command receiver 3 can listen to the content of the speech between the command issuer 1 and the determinate receiver 2.