Telephone exchange including less display elements than channels

Abstract

A telephone exchange accommodates a plurality of lines in a primary group of an Integrated Services Digital Network (ISDN), as well as a plurality of extension terminals, in which a plurality of channels constitute each line. Control is performed in such a manner that the status of a line of an extension terminal when this terminal is using one channel among the plurality thereof is indicated by lighting an Light Emitting Diode (LED) in the color green, the status of a line of an extension terminal when this terminal is not using any of the plurality of channels but all of these channels are being used by other terminals is indicated by lighting the LED in the color red, and the status of a line of an extension terminal when this terminal is not using any of the plurality of channels but some of these channels are being used by other terminals is indicated by flashing the LED in the color red. The flashing period of the flashing red LED is made to differ in dependence upon the total number of channels and the number of channels in use.

Dependencies are inferred from the claim text.