JP2814685B2 - Audio switching device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL APPLICATION The present invention selects and selects one audio signal from a plurality of audio signals.
The present invention relates to a voice switching device for holding and controlling.

2. Description of the Related Art Conventionally, this type of audio switching device is composed of a plurality of cross point circuits for connecting and disconnecting audio signals, and a control circuit for holding selection information and controlling the selection of the cross points.

FIG. 2 shows an example of a conventional voice switching device. In FIG. 2, reference numeral 11 denotes one of audio input terminals, and an input audio signal is guided to 12 cross points. 14 indicates an output amplifier. 13 is a control signal for each cross point.

In FIG. 2, a plurality of audio signals are respectively connected to audio input terminals. On the other hand, the selection data is converted into status information by the data holding circuit, and then becomes an individual cross point control signal corresponding to the cross point by the decoder, thereby performing cross point alternative selection control. When information that can directly control the individual cross points is given as the selection data, the data holding circuit and the decoder in FIG. 2 may not be necessary.

As described above, even the above-described conventional audio switching circuit can selectively hold one audio signal from a plurality of audio signals.

Problems to be Solved by the Invention However, the above-described conventional audio switching device has a problem that switching noise occurs due to DC bounce generated at the time of switching a cross point.

The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide an excellent audio switching device with less switching noise.

Means for Solving the Problems In order to achieve the above object, the present invention provides a mute circuit at the subsequent stage of the audio selection circuit, and when this mute circuit is selected for switching, the selection data held up to that time and the next held data are stored. Control is performed by a judgment output signal of a comparison circuit of newly given selection data as much as possible.

Operation The present invention has the following operation with the above configuration. That is, the selection data comparison circuit performs mute control at the time of selection switching only when the newly supplied selection data is different from the selection data up to that time.
Switching noise can be reduced.

Embodiment FIG. 1 shows the configuration of an embodiment of the present invention.
In FIG. 1, reference numeral 21 denotes one of audio signal input terminals, and the input audio signal is guided to a cross point 22. The audio signal selected by any one of the cross points 22 passes through the mute circuit 23 and is output by the output amplifier 24. The selection data for performing the selection control of the cross point passes through the data holding circuits 31 and 32 and is given to the decoder 48 to become each cross point control signal 44. 33 is a pulse delay circuit for delaying the holding pulse 47,
This is for giving a time difference between the output signal (selection data) 42 of the data holding circuits 2 and 32 with respect to the output signal (selection data) 41 of the data holding circuits 1 and 31. A data comparator 34 outputs a comparison output 45 when the output signals 41 and 42 are different. A waveform shaper 35 converts the comparison output 45 into a mute circuit control signal 46.

Next, the operation of the above embodiment will be described. The selection data of the cross point 22 is input to the data holding circuit 31 and held by the holding pulse 47. The holding output 41 of the data holding circuit 31 is held again by the holding pulse 43 delayed by the delay circuit 33, and becomes the holding output 42 of the data holding circuit 32. Therefore, the time difference given by the delay circuit 33 occurs for the value of the hold output 42 to become the same as the value of the hold output 41. The delay circuit 33 compares the held outputs 41 and 42 and outputs a comparison output when the values are different. That is, the comparison output 45 corresponding to the delay time of the delay circuit 33 is output only when the value of the control data held up to that point is different from the value of the newly given control data. The comparison output 45 is converted into a mute circuit control signal 46 by the waveform shaper 35 and controls the mute circuit 23. Therefore, if the delay time of the delay circuit 33 is set to be equal to or longer than the time until the DC bounce generated by the selection switching of the cross point 22 becomes stable, the mute circuit 23 operates during the generation period of the switching noise. Signal selection can be switched.
Further, when the old and new selection data are the same, the control of the mute circuit 23 is not performed, so that when the same cross point 22 is continuously selected, the sound signal is not interrupted.

According to the present invention, as is apparent from the above-described embodiment, the mute control is performed only when switching noise occurs by determining the new / old selection data.
This has the effect that the switching noise caused by the selection switching of the audio signal can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an audio switching device according to an embodiment of the present invention, and FIG. 2 is a schematic block diagram of an embodiment of a conventional audio switching device. 21 ... Audio input terminal, 22 ... Cross point, 23 ... Mute circuit, 24 ... Output amplifier, 31, 32 ... Data holding circuit, 33 ... Pulse delay circuit, 34 ... Data comparator, 35 ...
... waveform shaper, 41, 42 ... selection data, 43, 47 ... hold pulse, 44 ... cross point control signal, 45 ... comparison output, 46 ... mute circuit control signal.

Claims (1)

(57) [Claims] 1. A mute circuit provided at a subsequent stage of an audio selection circuit when selecting and holding an alternative audio signal from a plurality of audio signals, and a cross circuit held up to that time during switching control of the mute circuit. An audio switching device that includes means for making a determination based on point selection data and cross-point selection data held next to determine whether or not mute control is performed, thereby reducing switching noise.