method for optional demodulation of one or several, in particular two, mehrfachfrequenzumtastung combined fernschreibkanaele and schaltungsanordnung for implementation of the procedure

摘要

The selective demodulator, for demodulating one or more multiple-frequency-keyed combined teleprinter channels, distinguishes between signal and noise close to the theoretical limit (less than 1 dB difference) and does not require the counter to be reset in strict synchronism with the frequency keying. It also has precise frequency resolution. The counter, which receives the information signal after frequency conversion, counts to a given number and upon reaching it produces a pulse. The present number is less than the max. number of information signal periods occurring during one keying period. The counter is reset before the next keying period begins.