JPH0728232B2 - FM transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention provides a music signal reproduction output for a compact disc or the like by FM.
FM transmitter that transmits by radio wave.

2. Description of the Related Art Conventionally, when a music signal reproduction output of a compact disc or the like is transmitted by an FM radio wave and is received and reproduced by an FM receiver, the compact disc is played in stereo both when playing and when not playing.

Problems to be Solved by the Invention However, since the noise at the time of stereo demodulation of the receiver is larger than that in the case of monaural, the stereo signal is always transmitted / received in stereo even when the music signal of the compact disc such as stop, pause and skip is not reproduced. You can see the noise well. Especially when the source is a compact disc, there is a problem that stereo demodulation noise is annoying because the signal source noise is small.

In order to solve the above problems, the FM transmitter of the present invention is provided with a means for connecting and disconnecting a 19 kHz pilot signal,
When the music signal of the compact disc such as stop, pause, skip, etc. is not reproduced, this means is driven so that the pilot signal is not modulated and the FM radio wave is received by the receiver in monaural.

The present invention reduces unpleasant noise by transmitting and receiving in stereo when a music signal of a compact disc is reproduced and receiving monaural when a music signal is not reproduced by the above configuration.

Example An FM transmitter according to an example of the present invention will be described below with reference to the drawings. The drawings show a block diagram of an FM transmitter in one embodiment of the present invention.
In the drawings, 1 is a compact disc player, 2 is a pre-emphasis circuit connected to the compact disc player, 3 is a time division multiplex connected to the pre-emphasis circuit 2, 4 is an oscillator having an oscillation frequency of 38 kHz, and 5 is an oscillator 4. Is a divider for obtaining a 19 kHz pilot signal from, FM is an oscillator, 7 is an amplifier, 8 is an antenna, and 9 is a transistor for connecting and disconnecting the pilot signal. The music signal reproduction output of the compact disc player 1 is pre-emphasized by the pre-emphasis circuit 2, a composite signal is created by the time division multiplex circuit 3, injected into the FM oscillator 6, frequency-modulated, and transmitted from the antenna 8. 1a is a low level when the compact disc music signal such as stop, pause, skip is not played,
It is a terminal that outputs a high level when reproducing, and is connected to the base of the transistor 9.

In the FM transmitter configured as described above, when the compact disc music signal such as stop, pause, skip is not reproduced, the output terminal 1a is at a low level, the transistor 9 is non-conductive, and the output of the divider 5
Since the 19 kHz pilot signal is not injected into the FM oscillator 6, the pilot signal is not modulated. Therefore, at this time
When the radio wave from the FM transmitter is received by a receiver (not shown), the demodulator receives it in monaural. Next, when the compact disc is played back except for stop, pause, skip, etc., the output terminal 1a becomes high level and the transistor 9
Is conducted, the 19 kHz pilot signal is injected into the FM oscillator 6 and is modulated together with the music signal. Therefore, at this time, if the receiver receives the radio waves from the FM transmitter, the demodulator will receive and reproduce in stereo.

As described above, according to the present embodiment, the transistor 9 for connecting and disconnecting the 19 kHz pilot signal is provided to stop, pause,
By not conducting the transistor when the music signal of the compact disc such as skip is not reproduced, the FM radio wave is received by the receiver in monaural when the compact disc is not reproduced, and the unpleasant stereo demodulation noise can be eliminated.

As described above, the present invention is provided with a means for connecting and disconnecting the pilot signal of the FM transmitter, and does not modulate the pilot signal by driving the means when the music signal of the compact disc such as stop, pause and skip is not reproduced. By doing so, FM radio waves can be received by the receiver in monaural, and unpleasant stereo demodulation noise can be eliminated.

[Brief description of drawings]

The drawing is a block diagram of an FM transmitter according to an embodiment of the present invention. 1 ... Compact disc player, 3 ... time division multiplex, 4 ... oscillator, 5 ... divider, 6 ...
… FM oscillator, 9… Transistor.

Claims (1)

[Claims] 1. An FM transmitter for transmitting a music signal reproduction output of a compact disc or the like by FM radio waves, the frequency being 19 kHz.
A means for connecting and disconnecting the pilot signal is provided to prevent the pilot signal from being modulated by driving the above means when the music signal of the compact disc is not reproduced, such as stop, pause and skip, and the FM radio wave is received by the receiver in monaural. FM transmitter characterized by doing so.