CN2084265U - Frequency modulation stereophonic demodulator - Google Patents

Abstract

The utility model relates to a frequency modulation stereophonic demodulator which is used for the receiving and playback of frequency modulation stereophonic signals. The circuit of the utility model is composed of a frequency modulation stereophonic signals receiving circuit, an on-off self-control circuit and a power supply circuit. The input terminal of the on-off self-control circuit is the modified R.F. Head of a black and white TV in market whose frequency modulation within the scope of 88-108MH. The back plate of the casing of the frequency modulation stereophonic demodulator is provided with a jack which is used for the connection of the signals transmission cables of closed circuit television system, and can carry out automatic on-off according to the existence of input signals. The utility model is suitable for places which has the installation of the closed circuit television system, and replaces the existing wired broadcasting network and broadcast own frequency modulation stereophonic programs.

Description

Frequency modulation stereophonic demodulator

The utility model relates to a kind of electronic installation of f-m stereo acoustical signal that is used to receive and reset: the FM multiplex demodulator.

Along with the development of China's broadcasting and tv undertakings, common antenna and closed-circuit television system have been widely used in urban and rural residents' dwelling house.Improved the quality of reception of TV signal, and can provide the FM multiplex program to user terminal, enrich the people's free life, yet some public place or unit (for example park, school etc.) although cable radio network near the closed-circuit television system of our unit, the stereo signal source that can't utilize closed-circuit television system to provide all, still use old-fashioned loudspeaker, a riot of sound, influence broadcasting efficiency.

The purpose of this utility model is will develop a kind ofly can replace existing some cable radio network and receive and reset from the FM multiplex program of closed-circuit television system and can be according to having or not input signal and the FM multiplex demodulator of automatic switching.

The technical program is achieved in that by front panel, backboard and constitutes a FM multiplex demodulator at interior casing and the circuit that is contained in the casing, the FM multiplex demodulator circuit partly is made up of FM multiplex signal receiving circuit, switching on and shutting down automatic control circuit and power circuit 3, the input of switching on and shutting down automatic control circuit is the commercially available black and white television set tuner of adjustable frequency scope between 88～108MHz through repacking, and the casing backboard of FM multiplex demodulator has one to be used for the socket that is connected with signal-transmitting cable in the closed-circuit television system.The FM multiplex signal receiving circuit is by fm tuner, several parts of stereodecoder and power amplifier are formed (as shown in Figure 1), 23 pin that constitute the integrated circuit C * A1019 of fm tuner are connected to 1 pin of the integrated circuit TA7342P that constitutes stereodecoder through an electric capacity, 6 pin of TA7342P and 9 pin connect 8 pin and 1 pin of the integrated circuit BA328 that constitutes power amplifier respectively through an electric capacity, the switching on and shutting down automatic control circuit is by the black and white television set tuner through repacking, and several parts of intermediate level circuit, detecting circuit and switching circuit are formed (as shown in Figure 1).Intermediate level circuit constitutes three grades of transistor common-emitter amplifiers by transistor BG1, BG2, BG3, the collector electrode of BG3 is connected on the diode D2 of detecting circuit through an electric capacity, switching circuit is made of transistor BG4, BG5, BG6, BG4 and capacitor C 14 constitute a Miller integrator, BG5, BG6 constitute a Schmidt circuit, the base stage of BG4 is connected with the output of detecting circuit, and the collector electrode of BG6 is connected with relay J 1.

The operation principle of FM multiplex demodulator is such: when no f-m stereo acoustical signal is exported on the signal output cable of closed-circuit television system, tuner in the switching on and shutting down automatic control circuit does not receive signal, so intermediate level circuit no-output, detecting circuit also just is provided with direct voltage output, transistor BG6 in the switching circuit ends, be connected in the relay J 1 not adhesive on the BG6 collector plate, the FM multiplex signal receiving circuit in the FM multiplex demodulator does not have operating current, so do not work.When the output of f-m stereo acoustical signal is arranged on the signal-transmitting cable of closed-circuit television system, tuner is given intermediate level circuit with the signal that receives and is amplified, output one direct current voltage gave switching circuit after the delay of Miller integrator after signal after the amplification was given the detecting circuit detection again, make the Schmidt circuit upset, cause transistor BG6 conducting, being connected in the relay J 1 on the BG6 collector electrode has electric current to flow through, relay J 1 adhesive, power circuit provides operating current to the FM multiplex signal receiving circuit, fm tuner takes out the f-m stereo acoustical signal from the signal-transmitting cable of closed-circuit television, give that stereodecoder is discrete to go out original left and right sides acoustic energy signal, again after power amplifier amplifies, the stereo sound music program of grace of just from audio amplifier, resetting out.

As long as stereo set or high-quality radio-cassette player that the closed-circuit television system front end has high-quality, with their output signal by modulators modulate in the FM frequency range again with radiofrequency signal feed-in closed-circuit television system, be contained in system subscriber terminal with this FM multiplex demodulator and just can obtain satisfied stereo reproduction, this FM multiplex demodulator is installed in the cable radio network of park or school, machine left automatically when signal was arranged, machine closes automatically during no signal, use very conveniently, and can broadcast FM stereophonic broadcast that constituent parts manages by oneself and the colourful theatrical items of managing by oneself.

Embodiment: Fig. 2 of the present utility model is FM multiplex signal receiving circuit and power circuit, Fig. 3 is the switching on and shutting down automatic control circuits, and tuner uses commercially available KP-12-3, after repacking, the adjustable frequency scope is between 88-108MHz, during no signal, the detecting circuit of being made up of diode D1 and D2 among Fig. 3 does not have direct voltage output, and the transistor BG4 in the switching circuit ends, BG5 is saturated, BG6 ends, BG6 collector electrode no current, relay J 1 not adhesive.When the f-m stereo acoustical signal was imported, this signal was through BG1, BG2 in the intermediate level circuit.Three grades of amplifications of BG3, give D1 and D2 detection again, R14, R15, R16 and C12, a positive direct voltage is provided for after the filtering of C13 the BG4 in the switching circuit, because the effect of C14, the slow conducting of BG4, cause BG5 to end, the BG6 conducting, the BG6 collector electrode has electric current to flow through, relay J 1 adhesive, the FM multiplex signal receiving circuit power supply of power circuit in Fig. 2, pass through earlier by L1 by the f-m stereo acoustical signal that signal-transmitting cable in the closed-circuit television system is sent here, C1,12 pin of delivering to C * A109 collecting circuit behind the band pass filter that L2 and C2 form carry out high frequency and amplify, pass through again by L3, C01, the 9th pin of sending into IC after the shunt-resonant circuit frequency-selecting that C02 forms carries out mixing, obtain the intermediate-freuqncy signal of 10 megahertzes after the mixing, 14 pin output by IC, ceramic filter CP2 through 10 megahertzes carries out frequency-selecting, enter the FM intermediate frequency amplifier of 1C the 16th pin then, amplify the back and enter the FM frequency discriminator in 1C inside, the 2nd pin of iC links to each other with frequency discriminator, be connected to the frequency discrimination filter of 12.7 megahertzes, FM composite signal behind the frequency discrimination is from the 23rd pin output of 1C, composite signal by the output of C * A1019 the 23rd pin is imported by the 1st pin of stereo decoding circuit TA7342P, after amplifying, be sent to the phase discriminator of phase-locked loop, amplitude discriminator and stereo demodulator, final discretely from stereo composite signal go out an original left side, right-channel signals, respectively by 8, the output of 9 pin, carry out preposition amplification through integrated circuit BA328 again, integrated circuit HA1392 carries out power amplification, a left side, right-channel signals is given two 8 Europe respectively, the audio amplifier of 25W, the graceful stereo music of resetting out.

Claims (3)

1, a kind of FM multiplex demodulator, form by casing that comprises front panel, backboard and the circuit that is contained in the casing, it is characterized in that: the FM multiplex demodulator circuit partly is made up of FM multiplex signal receiving circuit, switching on and shutting down automatic control circuit and power circuit three, the input of switching on and shutting down automatic control circuit be one through the adjustable frequency scope of reequiping at 88～108MH _zBetween commercially available black and white television set tuner, the casing backboard has one to be used for the socket that is connected with signal-transmitting cable in the closed-circuit television system.

2, demodulator according to claim 1, it is characterized in that: the FM multiplex signal receiving circuit is made up of several parts of fm tuner, stereodecoder and power amplifier, 23 pin that constitute the integrated circuit C * A1019 of fm tuner are connected to 1 pin of the integrated circuit TA7342P that constitutes stereodecoder through an electric capacity, and 6 pin of TA7342P and 9 pin are connected to 8 pin and 1 pin of the integrated circuit BA328 that constitutes power amplifier respectively through an electric capacity.

3, demodulator according to claim 1, it is characterized in that: the switching on and shutting down automatic control circuit is by the black and white television set tuner through repacking, intermediate level circuit, several parts of detecting circuit and switching circuit are formed, intermediate level circuit, several parts of detecting circuit and switching circuit are formed, intermediate level circuit is by transistor BG1, BG2, BG3 constitutes three grades of transistor common-emitter amplifiers, the collector electrode of BG3 is connected on the diode D2 of detecting circuit through an electric capacity, switching circuit is by transistor BG4, BG5, BG6 constitutes, BG4 and capacitor C 14 constitute a Miller integrator, BG5, BG6 constitutes a Schmidt circuit, the base stage of BG4 is connected with the output of detecting circuit, and the collector electrode of BG6 is connected with relay J 1

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