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Telephone Talks Coder

Telephone Talks Coder

Signal coders are used for telephone negotiations encode. Fig.1- the circuit of simple coder. Coders produces the inversion of the low frequency signal. As a result a signal becomes illegible. But at the same time a signal is normally passed by the telephone channels. Clock pulse-generator DD2 produces impulses with frequency 7 kHz. Divider with frequency 3.5 kHz is collected on D – flip-flop DD3. Analog switchboard DD4 with a differential amplifier form balanced modulator. Input filter on the microcircuit DA1.1 has the bar of admission of 300…3000 Hz. The device has the function of both coder and decoder. Synchronization of two coders is not required, however at adjusting by the resistor R5 it is necessary to set identical frequencies of bearing on maximal legibility.

Telephone Talks Coder Circuit
(Click to enlarge the Circuit)

Literature: Magazine Радиохобби №4 1999.

added 24.02.08 01:46:23 | looked over 751 times