PURPOSE: To attain the waiting time guarantee in matching with an optional time length by setting the guarantee time corresponding to a control code and transferring the time to a low-order device in decording a time gurantee command character code.

CONSTITUTION: The time gurantee command character code * and time guarantee codes α, β indicating a multiple of one of fixed time lengths are prepared in correspondence to the control codes CR, LF by which a communication access means 1 performs the time guarantee. In transmitting the given control codes CR, LF, the time guarantee indication character code * and the time guarantee codes α, β are transmitted to a communication controller 2 in correspondence to the control codes CR, LF. In coding the time guarantee code * in the communication controller 2, the guarantee time given by a value indicated by the fixed time length (a) and the time guarantee codes α, β is set in correspondence to the control codes CR, LF and transferred to a printer 3.