JPS5853709Y2 - Track interval detection circuit for tape recorder cueing device - Google Patents

Description

[Detailed description of the invention] This invention relates to a song interval detection circuit for a device for cuing up songs recorded on a tape, which is used in a tape recorder, and some noise signals are recorded in the no-signal areas between songs. To provide a song interval detection circuit that is unlikely to malfunction even when searching for the beginning of a song when playing back a tape or a music tape with a low signal level during the song.

In general, in order to select and play six desired songs from a tape with many recorded songs, it is necessary to search for the beginning of the song by fast forwarding or rewinding. An automatic cueing device that detects a no-signal section between songs is provided to facilitate the cueing of a tape, and first performs high-speed playback by fast forwarding or rewinding, and when a no-signal section between songs arrives on the tape, It is now possible to detect this and automatically switch from high-speed playback to normal playback.

Some of these automatic song cueing devices play high-speed playback for one song to cue the song, or play multiple songs while counting the number of songs until they match the preset song number. There are some methods that do this, but in any case, it is possible to accurately detect the no-signal portion between songs during high-speed playback.
It must be something that is less likely to malfunction.

Figure 1 is a circuit diagram showing only the main parts of a conventional tape recorder equipped with a song cue device.
The reproduced signal is applied to a power amplifier 3 through a preamplifier 2 to drive a speaker 4.

Next, when starting a song, switch sb is closed and power supply B is supplied, so the song interval detector 5 is working, and the playback signal from the head 1 due to high-speed playback is passed through the preamplifier 2. After that, the signal is branched and applied to the inter-track detector 5, and when a no-signal part between tracks on the tape is detected, the track cue circuit connected to the inter-track detector 5 automatically switches from high-speed playback to normal playback. can be switched to

The button and switch Sa are recording and playback changeover switches, which carry out the well-known operation of changing the frequency characteristics of the preamplifier 2 by switching to the equalizer 6 for playback and to the equalizer I for recording.

However, such conventional song cue devices have various disadvantages when it comes to detecting no-signal sections between songs. Background noise is likely to be recorded, and if a noise signal is recorded in an area that should normally be a no-signal area, it may not be detected as an inter-song no-signal area when the beginning of a song is searched.

Therefore, if you want to prevent such malfunctions, it is necessary to use the inter-track detector 5.
It is best to set the no-signal detection level as high as possible, but some commercially available music tapes, especially classical music tapes, have extremely low signal levels during songs, so it is difficult to When the beginning of a song is found, the inter-song detector 5 is activated, causing a different malfunction from the above-mentioned one.

Setting the no-signal detection level of the inter-track detector 5 is extremely critical, and it is difficult to make it compatible with all kinds of recording tapes and with fewer malfunctions.

This invention was devised to improve the drawbacks of the conventional music cue device as described above, and FIG. 2 is a circuit diagram showing one embodiment thereof.

For this figure 2, 1 is the recording and playback head, 2 is the preamplifier, 3 is the power amplifier, 4 is the speaker, 5 is the inter-track detector, 6 is the playback equalizer, and I is the recording equalizer. The automatic level control circuit 8 (hereinafter referred to as AL)
(referred to as C circuit), and the ALC circuit 8 is a diode D1.
tD2, a capacitor C1tC2, a resistor R, and a transistor Tr1tTγ2, Sa is a recording/playback switch, Sb 1ssb 2. Sb
3 is a changeover switch for finding the beginning of a song.

Next, the operation of the circuit of this embodiment will be explained. First, in the case of playback, the playback output of the recording/playback head 1 is applied to the power amplifier 3 via the preamplifier 2, and is output to the speaker 4.
The preamplifier 2 is connected to the reproduction equalizer 6 by the changeover switch Sa, and has a low-range boost frequency characteristic.

Further, in the case of finding the beginning of a song, the reproduction signal of the recording and reproduction head 1 by high-speed reproduction is amplified by the preamplifier 2 and applied to the ALC circuit 8 by the switch 5b-1.

This signal is current-doubled and rectified by diodes D1 and D2, charged into a capacitor C1, and further DC amplified by a transistor Tγ1 through a resistor R, and then applied to the base of a transistor Tγ2.

By this, the transistor Tγ2 connected in parallel with the preamplifier 2 is connected? Since the vector-emitter resistance is reduced, the input impedance of the preamplifier 2 is reduced, and the level of the output signal of the preamplifier 2 is reduced.

That is, the average level of the input signal to the inter-song detector 5 is maintained at a substantially constant value by the control action of the ALC circuit 8, and the inter-song detector 5 is supplied with the power supply B by the switch 5b-2. When a no-signal portion between songs is detected on the tape, a song cue circuit operates to automatically switch the tape recorder from fast forwarding or rewinding high-speed playback to normal playback.

In addition, the ALC circuit 8 has its release time set so as not to follow a sudden drop in input level, and when finding the beginning of a song, a time constant approximately determined by the capacitor C1 and the resistor R is set on the tape. This is sufficiently longer than the time it takes to pass through the no-signal portion between songs during high-speed playback.

Next, in the case of recording, selector switch S is placed on preamplifier 2.
A recording equalizer T is connected by a to provide high frequency boost frequency characteristics, and a recording signal from the preamplifier 2 is applied to the same ALC circuit 8 as described above by a switch 5b-1.

Therefore, the recording signal is maintained at a level that prevents over-recording by the action of the ALC circuit 8, but since the tape speed is slower in recording than in high-speed playback, the switch 5b-3 controls the capacitor C1. The capacitor C2 is switched to a larger capacitor to make the time constant larger than in the cueing case.

In addition, in the conventional inter-song detector, since the change in the input signal is large, it was necessary to set the no-signal detection level as low as possible to avoid malfunction, but in the circuit of the embodiment, the inter-song detector 5 Since the average level of the signal applied to the sensor is kept almost constant, the no-signal detection level can be set higher than that of the conventional system.

In addition, since the ALC circuit 8 of the embodiment has a release time longer than the time required to pass through the no-signal area between songs on the tape during high-speed playback, it is possible to prevent noise signals recorded in the no-signal area between songs. However, a controlling effect works to lower the level.

Therefore, even when the beginning of a song is searched using a tape in which background noise or the like is recorded in the no-signal portion between songs, the inter-song portion can be efficiently detected.

Furthermore, when searching for the beginning of a song using a music tape such as classical music, even if the signal level in the song is low, the ALC circuit 80 level control action hardly works, so the relative average level of the signal is This will result in the same bundling as when the height has increased, and this part will no longer be detected as a no-signal part.

As described above, this invention uses the ALC circuit 8 to make the average level of the input signal to the inter-song detector 5 almost constant, and only when the signal level falls by a predetermined value from this average level, the signal is input to the inter-song detector 5. The no-signal detection level is set so that it is detected as a no-signal part between songs, and the control action of the ALC circuit 8 follows the reproduced signal during a song, but is made so that it is difficult to change for a no-signal part between songs. This prevents malfunctions related to the detection of between songs.

In addition, even when starting a song using a tape that has background noise recorded in the no-signal areas between songs, it is possible to accurately detect the gaps between songs. Even when a tape with a low signal level is used to locate the beginning of a song, malfunctions such as detecting this as a no-signal section are reduced.

In addition, since the ALC circuit for keeping the average level of the input signal to the inter-song detector almost constant and the ALC circuit for recording are shared and used by switching them with a switch, the cost required for this is minimal. It is small.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional tape recorder equipped with a track cue device, and FIG. 2 is a circuit diagram of a tape recorder equipped with a track interval detection circuit according to the present invention. 1...recording, playback head, 2...preamplifier, 3...
... Power amplifier, 4 ... Speaker, 5 ... Inter-song detector, 6 ... Playback equalizer, T ... Recording equalizer, 8 ... ALC circuit, D 1 * D 2 ... Diode ,C□. C2... Capacitor, R... Resistor, T 11 ,
Tγ2...transistor, Sa...recording, playback selector switch, Sb, 5b-1, 5b-2j 5b-3.
・Switch for starting the song.

Claims (2)

[Scope of utility model registration request] (1) Equipped with a playback head, a playback amplifier, and a detector for detecting a no-signal area between songs, when performing high-speed playback by fast forwarding or rewinding, and detecting a no-signal area between songs on the tape by the inter-song detector. In a tape recorder configured to automatically switch from high-speed playback to normal playback, the tape recorder is operated by the output signal of the playback amplifier to keep the average level of the input signal to the song interval detector approximately constant. An automatic level control circuit is provided, and a time constant circuit is provided in the automatic level control circuit so that the release time of the automatic level control circuit is longer than the time it takes to pass through a non-signal area between songs on the tape during high-speed playback. A track interval detection circuit for a cue device for a tape recorder, characterized in that: (2) The above automatic level control circuit is shared with the recording circuit of a tape recorder, and is switched by a switch for detecting a song and for recording, and the release time of the automatic level control circuit is changed depending on the song. A cueing device for a tape recorder as set forth in claim 1 of the utility model registration claim, characterized in that the time constant element is changed by a switch so that the time constant element is short in the case of cueing and long in the case of recording. Song interval detection circuit.