Information transmission device with frequency selection - compensates for difference in temp. between interrogation and reply units

摘要

The information transmission device has interrogation and reply units the latter reflecting the received interrogation signal back so that individual given frequencies specifying the information are selected. The received signal is used to provide a corresponding pulse train compared with a reference pulse train provided by the interrogation unit (AB). For each period of the interrogation signal, the first pulse of the first pulse train (4) is used to activate a clock generator (T) synchronised with the second pulse train (2) and having a relatively high frequency compared to the latter. The clock generator pulses control a frequency converter (U2) providing a third pulse train (5) with pulses lying central to all evaluation time points and fed to a comparator (A) also receiving the first pulse train (4).