PCM modulator for telemetry - has astable multivibrator with current sources in timing circuit controlled by variable

摘要

The PCM modulator, for telemetry, incorporates the function of preamplifier, contains stabilising components and is independent of supply voltage. The parameters being measured alter the duty factor of the pulses at the modulator's output. The modulator consists of an astable multivibrator (T1, T2) the bases of whose two transistors are cross-coupled to timing capacitors and to two current source transistors (T3, T4) controlled by the parameter being measured - controlled in terms of frequency, symmetry or duty factor. Several variations are possible built around this basic circuit.