This apparatus can be used to solve the problems of selecting ringing and keeping talk-secret among N extensions (1 is less than N is less than or equal to 10), which share a pair of subscriber's loop. It consists of the automatic ringing response unit of exchanger, the testing and analysing unit for secondary dialling pulses, local ringing selecting unit and the selecting unit for extension channels. The apparatus can be directly connected with subscriber's loop for various kinds of exchangers to act as an expanding device of telephone capacity in the house areas, countrysides or the organizations with less telephone services. |