Digital key telephone system

摘要

A digital key telephone system comprising evaluation test control means for performing an evaluation test of the system in co-operation with an external device. An external communication interface comprising a first signal path for transmitting a signal sent from the computer device, transferring the signal looped back by the evaluation test control means to the external computer device, a second signal path for looping back the signal sent from the computer device to the computer device without transferring the signal to the evaluation test control means and means for selectively switching the first and second signal paths under the control of the evaluation test control means.