JPS609968Y2 - Audio multiplex signal recording circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a recording circuit most suitable for use in recording television audio multiplex broadcasts.

The currently implemented television audio multiplex broadcasts include two-channel multiplex broadcasts such as bilingual broadcasts, etc.
There is also stereo multiplex broadcasting such as stereo music.

On the other hand, the stereo signal is transferred to a VTR. 2. Description of the Related Art As a recording circuit for recording with a tape recorder or the like, the circuit shown in FIG. 1 is conventionally known.

In FIG. 1, a portion of each output signal of an L channel line amplifier 1 and an R channel line amplifier 2 is applied to a level detection circuit 3, the level thereof is detected, and the L channel gain is controlled according to the detected level. The circuit 4 and the R channel gain control circuit 5 automatically control the gains of both channels.

In this case, the gains of both channels are controlled equally.

For example, if the input signal level of the L channel increases and
When compressing by dB, the R channel is also compressed by 5 dB at the same time so as not to impair the stereo feeling.

According to the recording circuit shown in FIG. 1, it is possible to record various stereo signals in addition to the stereo multiplex broadcast.

However, when recording the above-mentioned two-channel multiplex broadcast with this recording circuit, the level of one channel will be affected by the level fluctuation of the other channel due to the AGC operation described above, and therefore the signal will differ from the original signal. What happened will be recorded.

In view of the above problems, the present invention is designed to distinguish whether the input signal is a two-channel multiplexed signal or a stereo multiplexed signal, automatically switch the circuit according to the determination, and record both multiplexed broadcasts. This is what I did.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 2, a signal received by an antenna 11 is added to the audio circuit of a television receiver, and a tuner 12 extracts an audio multiplexed signal.

This signal is applied to the audio detector 14 through the W amplifier 13.

This detection output is applied to a pilot detection circuit 15 and also to a channel separation circuit 16.

The channel separation circuit 16 separates the two-channel signals by a known method and outputs a stereo multiplex signal or a two-channel multiplex signal to its output terminals 17 and 18.

The first channel signal obtained at the output terminal 17 is applied to an input terminal 19 provided on a tape recorder, VTR, etc., and the second channel signal obtained at the output terminal 18 is applied to an input terminal 20.

The first channel signal is applied to the magnetic bed 27 through the gain control circuit 21, the line amplifier 23, and the recording amplifier 25, and is recorded on the magnetic tape 29.

At the same time, the output level of the lineup 23 is detected by the level detection circuit 30.

The second channel signal is transmitted to the magnetic head 2B through a gain control circuit 22, a line amplifier 24, and a recording amplifier 26.
and recorded on the magnetic tape 29.

At the same time, the output level of the line amplifier 24 is detected by the level detection circuit 31.

On the other hand, the pilot detection circuit 15 detects whether the received signal is an audio multiplex signal, a stereo multiplex signal, or a two-channel multiplex signal.

As is well known, for stereo multiplex signals, for example, 55.12
A pilot signal P obtained by amplitude modulating a 5 KHz subcarrier at 982.5 Hz is included.

For example, 55.125KH for 2 channel multiplex broadcasting.
It includes a pilot signal PB that amplitude modulates the subcarrier of z using 922.5H2.

In this embodiment, the opening and closing of the switch circuit 32 is controlled depending on whether the pilot signal detected by the pilot detection circuit 15 is Ps or P.

That is, when a stereo multiplex signal is received and a pilot signal P is detected, the pilot detection circuit 15 outputs a signal that closes the switch circuit 32.

As a result, the level detection circuit 30.3 of both channels
According to the level detected in step 1, AGC is applied so that the levels of both channels are controlled equally.

Further, when a two-channel multiplexed signal is received and a pilot signal Pa is detected, the pilot detection circuit 15 outputs a signal that opens the switch circuit 32.

Therefore, in this case, both channels are connected to independent AGs.
C, the problem described in FIG. 1 is improved, and signals of both channels that are faithful to the original signals can be recorded.

Note that the pilot detection circuit 15 detects the pilot signal Ps=
The configuration may be such that the switch circuit 32 is opened or closed when one of the PBs is detected.

The present invention includes a first recording system and a second recording system for recording a first channel signal and a second channel signal obtained from a stereo multiplex signal or a two-channel multiplex signal, and the first and second recording systems. A first signal level detection circuit 30 and a second level detection circuit 31 that respectively detect signal levels.
and a first gain control circuit 21 and a second gain control circuit 22 that control the gains of the first and second recording systems, respectively;
a discriminating circuit 15 for determining whether the input signal is the two-channel multiplexed signal that is the stereo multiplexed signal;
and a switch 32 which connects or opens the output terminals of the second signal level detection circuits 30 and 31 to each other according to the discrimination signal of the discrimination circuit 15, and when the input signal is the stereo multiplex signal, , the switch 32 is operated in the connection direction so that the first and second gain control circuits 21.22 are commonly controlled by the outputs of the first and second signal level detection circuits 30.31. When the input signal is the two-channel multiplexed signal, the switch is operated in the open direction, and the first gain control circuit 21 is controlled by the output of the first signal level circuit 30. The present invention relates to an audio multiplex recording circuit characterized in that the second gain control circuit 22 is controlled by the output of the second signal level detection circuit 31.

Therefore, according to the present invention, when receiving a stereo multiplexed signal, it is possible to record without impairing the stereo feeling, and when receiving a two-channel multiplexed signal, each channel signal can be recorded without being affected by the other channel. Can be recorded.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an example of a conventional recording circuit;
The figure is a circuit system diagram showing an embodiment of the present invention. In addition, in the symbols used in the drawings, 15...
...Pilot detection circuit, 16...Channel separation circuit, 21.22...Gain control circuit, 23.24
...Lineup, 25.26...Recording amplifier, 27.28...Magnetic head, 30,
31...Level detection circuit, 32...Switch circuit.

Claims (1)

[Scope of utility model registration request] A first recording system and a second recording system that respectively record a first channel signal and a second channel signal obtained from a stereo multiplexed signal or a two-channel multiplexed signal, and a signal level of the first and second recording systems. a first signal level detection circuit and a second signal level detection circuit for detecting the signals, respectively; a first gain control circuit and a second gain control circuit for controlling the gains of the first and second recording systems, respectively; A discrimination circuit for discriminating whether the input signal is the stereo multiplexed signal or the two-channel multiplexed signal, and the output ends of the first and second signal level detection circuits are connected to each other according to the discrimination signal of the discrimination circuit. When the input signal is the stereo multiplexed signal, the switch is operated in the connection direction, and the output of the first and second signal level detection circuits is used to detect the signal level. The first and second gain control circuits are controlled in common, and when the input signal is the two-channel multiplexed signal, the switch is operated in the open direction to control the first signal level circuit. A recording circuit for audio multicast transmission, characterized in that the first gain control circuit is controlled by the output of the above-mentioned signal level detection circuit, and the second gain control circuit is controlled by the output of the second signal level detection circuit. .