| 摘要 |
1. Receiver in a system for the transmission of pulse signals, in particular of remote control signals, by electromagnetic radiation, in particular infrared radiation, of the type in which the radiation itself or a carrier is modulated by pulses of constant amplitude coded in predetermined manner, the receiver comprising in cascade : a detector stage (1) for detecting said radiation of the type comprising a resistive voltage divider (2, 3, 4), one of the branches of which comprises a detector element (2) whose resistance and/or current varies in dependence upon the intensity of the radiation which it receives, a preamplifier (10) of the band-pass type whose pass band includes the frequency of the carrier or the frequency equal to the reciprocal of twice the duration of the pulses when the latter is constant, and comprising a plurality of stages in cascade each equipped with a transistor (11, 16, 22) in common-emitter connection whose emitter circuit comprises a circuit arrangement for automatic biasing made up of a resistor (13, 20, 27) and a capacitor (14, 21, 28) connected in parallel and whose base circuit comprises a biasing circuit of the type of a resistive voltage divider (2-3-4, 17-18, 24-25), a stage (30) for shaping the received pulses and an output stage (40) adapted to feed a decoder with pulses modulating the radiation or the carrier, characterized in that the respective values of the resistors (20, 27) and the capacitors (21, 28) respectively equipping the emitter circuits of the transistors (16, 22) downstream of the input stage (11) of the preamplifier (10) are chosen so as to form pulse integrating circuits whose discharge time constants are of an order of magnitude comparable to the minimum duration of the interval between two successive pulses of a pulse train constituting the signal modulating the radiation or the carrier in order that the automatic additional biasing of the mitter with respect to the base obtained by the rapid recharging of the capacitor by each pulse received depends on the amplitude of said pulse and retains within said interval a value sufficient to eliminate or weaken parasitic pulses which would be produced in the course of the transmission of this train in place of minimum time spacing pulses.
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