JPS5918765B2 - tape recorder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape recorder having a compander system that compresses the level during recording and expands and restores the level during playback.

The first block diagram of a conventional general compander system is
Shown in the figure.

In FIG. 1, the recording system includes a level compression circuit consisting of a compression control signal system T that generates a control signal for level compression and a gain control circuit 6, and the input signal supplied from the input terminal 1 is sent to the level compression circuit. The signal is level-compressed and recorded on the magnetic tape 3 by the recording head 2. On the other hand, during playback, the compressed signal reproduced by the playback head 4 is expanded by a level expansion circuit consisting of an expansion control signal system 9 and an expansion gain control circuit 8, and is restored to the original signal and taken out from the output 5. . With this conventional method, the signal recorded on tape is completely indistinguishable from a normal recording signal that has not been compressed, so in order to playback correctly when compressed recording is performed, it is necessary to make sure that the tape is compressed recording. In addition, during playback, the user must judge from the tape display and manually switch on/off the playback expansion circuit and select the expansion ratio. Another drawback was that if there was no recording format indication on the tape, proper switching could not be performed, and it was completely unclear whether or not correct playback was being performed. An object of the present invention is to eliminate the above-mentioned drawbacks, and to detect whether a recorded tape is a normal recording or a compressed recording by playing the recorded tape with a tape recorder, without requiring the user's intervention. To provide a tape recorder having a function of automatically switching to a proper reproduction system and displaying without any trouble.

The present invention provides a tape recorder having a compander system, in which a pilot signal for identifying compressed recording or normal recording is used as an audio signal track during recording.

The idea is to record on a separate recording track, and during playback, detect the pilot signal and automatically switch between expanded playback and normal playback, and also display it. FIG. 2 shows a block diagram of an embodiment of the present invention.

The conventional program shown in Fig. 1 is equipped with a pilot signal generator 14 and a dedicated track recording/\\2, which simultaneously records a pilot signal indicating the companding ratio during compression recording, and outputs the pilot signal during playback. If it is recorded on a dedicated track, it is detected by the playback mode 13, and the switching circuit 15 is activated to automatically switch and display the playback system. A specific circuit diagram of the pilot signal generator 14 is shown in FIG.

This circuit is composed of a well-known CR oscillator, and is
0 represents an oscillation transistor, 21 represents an output adjustment variable resistor, and 22 represents an output terminal. This circuit obtains an oscillation output of about 15 Hz, which is outside the audio band. The +B power switch is linked to the recording switch and operates only during compressed recording. Next, a specific circuit diagram of the switching circuit 15 is shown in FIG.

In the figure, 28 is a terminal for receiving a signal from the reproducing head 4, 29 is a terminal for receiving a signal from the expansion gain control circuit 8, and 30 is a terminal for receiving a signal from the pilot signal reproducing head 13. 31 is an amplifier for amplifying the pilot signal, and 32 is a voltage doubler rectifier circuit.

Incidentally, the capacitor 33 and the resistor 34 form a signal holding circuit, which absorbs signal fluctuations due to tape dropouts and the like, and prevents malfunctions. Reference numeral 35 is a well-known Schmitt circuit, which increases the input impedance of the transistor 38 that drives the relay circuit 36 to stabilize the operation, and prevents the brightness of the display lamp 37 from changing depending on the input level.

Next, a block diagram of a second embodiment of the present invention is shown in FIG.

In the figure, the same parts as in FIGS. 1 and 2 are given the same reference numerals. This second embodiment uses a compression control signal during compression recording as a pilot signal for automatic switching. Further, in FIG. 5, the pilot signal based on the control signal is simultaneously recorded with the audio signal by the recording head 12 directly on a dedicated track during recording, and is detected by the playback head 13 during playback. Next, a block diagram of a third embodiment of the present invention is shown in FIG.

The present example is a tape recorder that automatically switches between normal recording and playback with a companding ratio of 1:1 and companding recording and playback with a plurality of companding ratios, for example, 2:3 and 3:4. FIG. 6 is an example in which this is applied to FIG. 5. In the figure, 16 indicates a compression ratio switching switch, and 17 indicates an expansion ratio switching circuit. As a pilot signal during recording, when the companding ratio is 2 to 3, the compression ratio changeover switch 16 modulates a 2 KHz carrier wave with a compression control signal, and when the companding ratio is 3 to 4, a 5 KHz carrier wave is used. The FM modulated signal is sent to the recording head 12. During playback, it is demodulated and used as an expansion control signal, and the expansion ratio switching circuit 17 determines the presence or absence of a pilot signal and the carrier frequency, and switches the expansion ratio of the expansion control signal system 9 to output audio at an appropriate expansion ratio. The signal is level-expanded and restored. In addition, as another method for the pilot signal in the third embodiment, a 3KHz carrier wave is used as a compression control signal for the pilot signal during recording.
It is also conceivable to use M-modulated signals and multiplex and send a single frequency identification signal outside the band of the compression control signal as a compression ratio identification signal.

During playback, if there is no control signal, the expansion ratio is 1:1.
, when there is a control signal, the companding ratio is identified based on the frequency of the multiplexed identification signal, and the audio is restored by switching to an appropriate expansion ratio. As described above, the present invention eliminates the conventional troubles of determining the recording system of the tape to be played back, switching the playback system accordingly, or specifying the recording system on the tape during compression recording. This makes it possible to provide a tape recorder with very good operability.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a tape recorder having a conventional general compander system, Fig. 2 is a block diagram showing a first embodiment of the present invention, and Fig. 3 is a pilot signal used in the embodiment of the present invention. FIG. 4 is a circuit diagram of the automatic switching circuit, FIG. 5 is a block diagram showing a second embodiment of the invention, and FIG. 6 is a third embodiment of the invention. It is a block diagram. 1... Audio signal input terminal, 2... Recording head) 3... Magnetic tape, 4... Playback head, 5... Output Terminal, 6... Compression gain control circuit, 7... Compression control signal system, 8
...Extension gain control circuit, 9...Extension control signal system, 12...Pilot signal recording head, 13...Pilot signal reproducing head, 1
4...Pilot signal generator, 15...Switching circuit, 16...Compression ratio selection switch, 1
7... Body tension ratio switching circuit.

Claims (1)

[Claims] 1. In a tape recorder equipped with a compander system that performs level compression during recording and expands and restores during playback, the recording system includes a means for generating a pilot signal for identifying level compression, and a means for generating a pilot signal for identifying level compression, and a means for converting the pilot signal into a level compressed audio signal. A pilot signal recording head separate from the recording head.
and a means for simultaneously recording the audio signal on a track different from the audio signal track; and a means for detecting the pilot signal to determine level compression in the playback system, and a signal for level compression based on this determination signal. means for selectively switching between a circuit for reproducing an ordinary audio signal that is not compressed and a circuit for decompressing and reproducing the level-compressed audio signal; and a circuit for reproducing the level-compressed audio signal using the determined signal. A tape recorder comprising: a means for displaying that a tape recorder is present;