PURPOSE: To confirm easily the normality of a channel in a short time by utilizing an input disconnection detection and display function and an idle signal transmitting function of a spatial split type exchange.

CONSTITUTION: Selectors A, B are thrown to the test position, a talking line connected already to an input terminal INO is connected to an external device TST, then a link of an SW20 is changed for connection by a general test program in the order of incoming terminal XO → outgoing terminal YO, ∼ incoming terminal XO → outgoing terminal Yn by the switch connection section. An idle signal from a preceding device lights an LED because of the input is disconnected. When the link of incoming terminal XO → outgoing terminal YO is set by the test program, a test idle signal via the selector B is inputted to the selector A via an external terminal TST, input terminal INO, gates GA, GB of an FO50, the incoming terminal XO, the outgoing terminal YO, a gate GC of an RO60 and a test terminal T; a DET detects the presence of input and the LED is turned off.