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摘要

Apparatus for ascertaining an overlap prior to transfer of code digits being interpreted in a telephone exchange is described. A dial control device and a counting chain storing dialed code digits are provided for each subscriber and/or local repeater. A switching element allocated to each dial control device controls, upon expiration of a time determined by a clock pulse, the triggering of the transfer of a code digit from the counting chain as a result of a signal identifying the end of a digit, and transmits as a function of a clock pulse a test signal to a conductor leading to corresponding switching elements of other dial control devices. If one of the other dial control devices is simultaneously operative, the switching means associated therewith, being rendered operative by said test signal, causes blocking of retransmission of code digits to the digit interpretation device.