TEST DEVICE

PURPOSE:To confirm a function of an interface unit by setting a step for smoothing a signal varied periodically and a step for make the smoothed signal to a ready signal at a terminal. CONSTITUTION:When test devices 8 and 9 are connected to MODEMs 1, 2 and the electric source of MODEMs 1, 2 is inputted, a timing signal RT from timing generating circuits 101 and 201 of MODEM 1, 2 is added to the devices 8 and 9. The signal RT is periodically varied, but is rectified and smoothed by diodes 85 and 95 and capacitors 86 and 96. Next, a terminal-ready signal ER is added to MODEMs 1, 2 from the devices 8, 9 by setting a circuit constant so that the signal may exceed the prescribed level. Thus, in case of confirmation of function of interface unit for MODEMs 1, 2, swtich operation for the signal ER isn't necessary. By simplly connecting the devices 8, 9 to an interface device, confirmation of function thereof and test operation can be easily done.