PURPOSE: To simplify a circuit by shifting to execution of a test program if a preparation completion display switch turns on when an electric power source switch is turned on, and executing an on-line connection by the subsequent on when said switch is not turned on.

CONSTITUTION: When a switch (SW)2 of a power source 1 is turned on in a state that an on-line setting SW12 is turned on, a microprocessor 4 reads SW information from an input port 9, and decides that a simple body test is designated. A form exists and cover closed state is read from the input port 9, a test program of an ROM5 is started, a data is outputted to an output port 8, a pulse motor is driven 11, a printing head is driven by synchronizing with a rotation of the pulse motor, and a character pattern contained in the ROM5 is outputted and printed. When the power source SW2 is turned on in a state that the SW12 remains opened, and thereafter, the switch 12 is turned on, the operation is shifted to an on-line processing with an external circuit. In this way, an exclusive switch and an exclusive control part for a test are not required, and the circuit is simplified.