JPS61126879A - Automatic output switching circuit - Google Patents

Abstract

PURPOSE:To obtain a TV set by which the output of a stereo or a MONO broadcast is possible to be outputted at an output terminal by providing a means to turn over a function change over switch to a stereo demodulation's side when SAP broadcast isn't executed by a noise component and a discrimination output. CONSTITUTION:In terms of a detection signal, 'H' level is outputted when SAP signal is generated, and in terms of the noise component, a nozzle detector is not actuated when a signal is given and the output of detection becomes 'H'. When SAP broadcast isn't made, the output of SAP carrier detector 10 becomes 'L' or 'H' because noise is detected by error. The output of a noise detector 11 becomes 'L' to detect the noise. Therefore, the output of AND circuit 12 becomes 'L' and a switch 15 is turned on. The output of an inverter 13 becomes 'H', and a switch 14 is turned off. An output signal from matrix 7 is outputted to the output terminal independently to a function change over switch 9. Thus, as long as either the SAP broadcast and the stereo broadcast exists, a sound 1 signals is outputted to the outputted of the TV set to make it easy to operate it.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an automatic output switching circuit in a TV audio multiplex receiver, and particularly to an automatic switching circuit applied to audio multiplex broadcasting broadcast in the United States.

(Prior Art) A conventional device of this type is shown in FIG. In the figure, 1 is S A P (S eoarate A
udi.

B-P-F, 2 that passes the P roaraa+) band
is a detector that detects SAP modulated waves, 3 is a dbx noise reduction decoder, 4 is an L-P-F that cuts frequencies above the sub-signal (L-R) band, and 5 is a (L-R) modulated wave. A detector for detecting waves, 6 a dbx decoder, 8 an L-P-F that cuts the main signal (L+R) band and above,
7 is a matrix circuit that performs 7 trixes of the (L+R) signal and the (LR) signal; 9 is a function changeover switch that switches the detection output between the dbx decoder 3 and the matrix 9; In such a configuration, when there is SAP broadcasting, the composite signal includes the SAP component, and the B.P.
Only the SAP signal is taken out by Fl, demodulated by a detector 2, and the demodulated signal that has passed through a dbx decoder 3 is supplied to a changeover switch 9. Also, when broadcasting in stereo, L
-P-F4 extracts the (L+R) signal, (shi-R) signal, pi, and lot signals, the detector 5 demodulates the (L-R) sub-signal, and the demodulated signal that has passed through the decoder 6 is sent to the matrix circuit. Enter 7. On the other hand, only the (L+R) main signal is taken out at L-P-F8 and input to the matrix circuit 7.

This matrix circuit 7 separates the R stereo signal and supplies it to the function changeover switch 9. A changeover switch 9 switches between SAP broadcasting and stereo broadcasting and sends it out to the subsequent stage.

(Problems with the prior art) Since the conventional device is configured as described above, for example,
When the function selector switch is set to the SAP position, nothing will be output when the SAP broadcast ends, causing the user to think that it is a malfunction. Also SA
After the P broadcast ended, the user had to perform an operation to switch to another positive control.

(Purpose) This invention was made in order to eliminate the drawbacks of the conventional ones as described above.When there is no SAP broadcast, the output of stereo or MONO broadcast is sent to the output terminal regardless of the position of the function selector switch. The purpose is to provide a TV receiver that can output.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. In FIG. 1, numerals 9 to 9 are the same as the conventional structure shown in FIG. To explain the added parts in Fig. 1, 10 is a detector that detects the presence or absence of the SAP carrier signal, and 11 is a noise detector. There is a possibility that the detector 10 may mistake the passing noise component for the SAP carrier wave signal and erroneously detect it, so the noise is detected in order to prevent this. 12 is an AND circuit of the outputs of the SAP'I11 transmitting wave detector 10 and the noise detector 11; 15 is an electronic switch that opens and closes with the output of the AND circuit 12; 13 is an inverter that inverts the output of the AND circuit 12; 14 is the inverter 1
It is an electronic switch that opens and closes with 3 outputs. In this configuration, its operation will be explained. The operations of the switch 8-P-Fl to the changeover switch 9 are the same as in the prior art, and their explanation will be omitted. The SAP carrier wave detector 10 detects the level of the carrier wave of the SAP signal that has passed through B-P-Fl. This detection output is at the rHJ level when the SAP signal is present. Further, when there is a noise component signal, the noise detector 11 does not operate, and the detection output becomes rHJ. Therefore, since both inputs are rHJ, the output of the AND circuit 12 is rl
(J, and the switch 15 is closed. At that time, the output of the inverter 13 becomes rLJ, and the switch 14 is opened. Therefore, the signal selected by the function changeover switch 9 is output to the output terminal.

Next, when there is no SAP broadcast, the SAP carrier wave detector 10
Since the output of rLJ or noise is erroneously detected, rI-I
Become J. On the other hand, since the noise detector 11 detects noise, its output becomes "L". Therefore, the output of the AND circuit 12 becomes rLJ, and the switch 15 becomes in between. Further, the output of the inverter 13 becomes rHJ, and the switch 14 is closed. Therefore, the function changeover switch 9 is attached to the output terminal.
The output signal from the matrix 7 is output regardless of.

(Effect) As described above, according to this invention, SA can be achieved with or without SAP Shinkyu.
In addition to cutting off the P circuit output, we shorted the function selector switch so that the stereo signal was always output when there was no SAP signal, so as long as there was either SAP broadcast or stereo broadcast, the TV receiver Since an audio signal is output to the output, the operation is easy for the user, and there is no risk of it being mistaken for a malfunction.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of an automatic switching circuit for an audio multiplex signal according to the present invention, and FIG. 2 is a diagram showing the configuration of a conventional audio multiplex signal.

Claims (1)

[Claims] A TV audio multiplex receiver that demodulates SAP broadcasting and stereo broadcasting, and selects and switches the demodulated output using a function changeover switch,
Means is provided for detecting the presence or absence of a carrier wave signal of broadcasting, and for discriminating between a noise component and a previous carrier wave signal, and for switching the function changeover switch to the stereo demodulation side when there is no SAP broadcast based on the detection and discrimination output. Automatic output switching circuit for a TV audio multiplex receiver.