Simple devices for video equipment. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Телевидение

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Today, the presence of two or more TVs is no longer a rarity. However, when they are used together, a number of problems arise, for example, with connecting an antenna or a VCR / video player. The proposed two devices make it relatively easy to solve them.

"LOW FREQUENCY" AUDIO AND VIDEO SPLITTER

A splitter can be used if, for some reason, a VCR or video player cannot be connected to two or more TVs via antenna inputs, i.e., at a "high frequency". It allows you to connect them at the so-called "low" frequency.

Although in [1] a similar device has already been considered, however, it has disadvantages that limit its wide repetition: the presence of a rare (especially for the province) imported microcircuit and bipolar power supply.

The device described here, the schematic diagram of the video channel of which is shown in Fig. 1 is easier to manufacture than the one mentioned above. It should be said, of course, about the audio channel. It is known that the audio output of a VCR or video player is designed for a load whose resistance exceeds 1 kOhm. Such an audio output is connected directly to the parallel-connected audio inputs of TVs, the input impedance of which is 47 ... 50 kOhm. Therefore, the audio channel is not shown in Fig. 1.

However, the video output of a VCR or video player is rated for 75 ohms, which corresponds to only one video input. Therefore, to connect two or more TVs, an isolation is required. For this purpose, two emitter followers are used similarly [2]. Their input impedance is high, so you can increase their number and connect up to six TVs.

To replace the KT972A transistors, any of the same series, as well as from the KT927, KT940 series, are suitable.

Resistors MLT, S2-33, S2-23 or similar and oxide capacitors K50-6, K50-16 or imported can be used in the device. The 12 V power supply must be rated for at least 100 mA.

The splitter is connected to the video equipment with a shielded cable through "tulip" connectors. A thin RK-75 antenna cable is also suitable.

IR REPEATER

This device can be used if the VCR/Video Player is already permanently connected via a splitter to two TVs in different rooms as shown in fig. 2. It is necessary to control the equipment with the remote control, being both in one and in another room.

The advantage of the repeater is that it fits all remote control standards Using the repeater, you can not only control the VCR/video player while playing a video, but also control the video in another room. You can also control both TVs.

The repeater receives the IR signal from the remote control of the VCR/video player or TV in one room, amplifies it and emits it in the second room where this equipment is installed. The signal is sent from one room to another via a cable, as shown in Fig. 2.

The repeater's IR receiver is placed in the room where the VCR/video player is supposed to be controlled. The repeater uses an industrial IR receiver PI-5, which is used in TV sets of the fourth and fifth generations. Any other industrial or home-made IR receiver without demodulation is also suitable (this is important), for example, on a TVA2800 or KR1056UP1 chip.

A variant of the circuit diagram of the device when using the PI-5 IR receiver is shown in fig. 3,a, and when using a receiver assembled on a TVA2800 chip, - in fig. 3,6. From the output of the IR receiver, the signal goes to the IR transmitter, made on one transistor, two resistors (VT6, FM5, R16 - in Fig. 3, a, VT1, R1, R3 - in Fig. 3, b) and LED HL1. The NI IR emitter is placed in a room containing a VCR/video player and one of the TVs, and it must be pointed at the object and rigidly fixed. The mounting location is chosen so that no one can accidentally interfere with the passage of the IR signal (for example, high on the wall under the ceiling). The emitter is connected to the device with any shielded cable.

In the device, the KT814A transistor can be replaced with any of the KT816, KT818 series. IR emitter AL156A can be replaced by any of the series AL 147, AL 165. Resistors MLT, S2-33, S2-23 or similar can be used in the device.

Literature

1. Nechaev I. Splitter of video and audio signals. - Radio, 1999, No. 1, p. 13.
2. Rodin A. et al. Repair of foreign TVs. Issue. 22. - M.: Solon-R, 1999, p. 31-35.

Author: I.Smirnov, Orel

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