Classification of additional devices for digital TV set-top boxes

Digital TV set-top box attachments, also known as set-top box companions, or digital TV companions, are also referred to as set-top box audio and video distributors.

Its function is to extend the function of a digital TV set-top box or other machines such as satellite receivers, DVD players, etc., which can be used for multiple TV sets to be viewed, and can be remotely controlled from different places. Without the additional purchase of a set-top box auxiliary unit and the additional payment of viewing fees (editors note that multiple TV sets can only watch the same channel). Just like the set-top box is installed in every room and on every TV, it is equally convenient to watch and operate in front of each TV. With the increasing popularity of set-top boxes, the use of set-top box attachments is becoming more and more extensive, which has also spawned a new product and a new industry.

The main principle of the additional device for digital TV set-top boxes is that the first is to remotely control the set-top box, and the second is to transmit the audio and video signals output by the set-top box to the TV or monitor in each room by wired or wireless means.

There are three types of structure: the first type is all-wire type, as shown in Figure 1, the infrared remote control signal and the RF signal output from the set-top box are transmitted to other TV sets through closed-circuit TV lines, and each terminal has an infrared Receive head.

The second type is similar to the first type, but the infrared remote control part realizes wireless remote control through a dedicated wireless transceiver module, and then converts the audio and video output signal of the set-top box into a radio frequency signal, and then connects this signal to each room through a distributor TV, just like the original CATV cable transmission method. Since the infrared receiving transponder is independent, expansion is very convenient. The third category is shown in Figure 2. The remote control method is the same as the second category. It is wireless, and the audio and video signals output by the set-top box are forwarded through low-power wireless. Generally, the 2.4GHz high frequency band is used to receive demodulated audio and video signals for each room TVs are watched in the AV state, and there are 4 channels of frequency bands for users to choose, so as to avoid interference with the same frequency band machine working at the same time, the audio design also meets the current consumption level, and is a broadband low-noise stereo. This method is more convenient to receive and expand, but the cost is higher. For example, the mobile DVD recently launched by Malata and Shinco has realized the wireless viewing of cable TV. The above three methods all use the remote control of the original set-top box. You can wirelessly control the set-top box in different rooms. You can also add a universal set-top box remote control to each TV set, which is suitable for promotion in ordinary households.

Here is a DIY set-top box attachment device suitable for the majority of electronic enthusiasts to make, which is characterized by low cost and easy installation and use. Due to the modularization, the infrared receiving and forwarding and audio and video conversion parts have been installed, and there is also a stylish appearance. All electronic enthusiasts need to do is to disassemble the remote control of the original set-top box and weld three wires as required, so anyone who knows a little bit about electronic technology can be modified, and remote control and signal transmission functions can be realized without debugging. . The block diagram of the working principle of the complete circuit is shown in Figure 3.

The complete set of DIY set-top box additional device is composed of two parts: the remote control transmitter A and the set-top box additional device receiving conversion part B: the remote controller transmitter A, mainly adds a wireless transmission module Tx-3 in the original set-top box remote control. The shape is shown in Figure 4. The size is 18mmX18mmx8mm. It has a transmitting antenna and three leads. Its function is to transmit the commands issued by the remote control not only through the original infrared medium, but also through the TX-3 module. The infrared remote control method of the original remote control is changed, and the remote control distance is increased. The distance can be remotely controlled indoors. The distance can reach 50 meters, which is enough to realize remote control of the set-top box anywhere in a 100 square meter home. During the modification, connect the three leads of the Tx-3 module to the positive pole of the remote control battery according to the red wire, the negative pole to the blue wire, and the yellow wire (which is the data input terminal) to directly connect the infrared luminous tube inside the remote controller to push the base of the triode. Or the output pin of the remote control integrated circuit (such as the pin ⑦ of the AS6122 integrated circuit in the STBl-1000 series digital set-top box remote control of PST). Because of the small size of the T & TImes; -3 module, it is easy to designate its installation country in the remote control. As long as the wiring is correct, install the module and lead out the transmitting antenna, the wireless remote control will be modified. If you don't want to use the original remote control of the set-top box for modification, you can also purchase a universal set-top box remote control for modification. Just before the modification, you must adjust the remote control to the normal set-top box according to the instructions, and then use the transmitter module to press the above Method for modification.

The receiving and converting part B of the accessory set-top box accessory device matched with it is composed of a data receiving infrared repeater module IR-RX, an audio-video conversion radio frequency box RF-H radio frequency amplification circuit, a power converter, and a 7805 voltage regulator circuit. The data receiving infrared forwarding module lR-RX is to restore the received wireless signal of the remote controller into an infrared remote control signal to control the set-top box. It already includes a receiver corresponding to the transmitting part, an infrared modulator, an infrared luminous tube, and a driving circuit, stable Voltage circuit, etc., its appearance size is 65mm & TImes; 18mmx5.5mm. The use voltage is 7 ~ 9V, the shape is shown in Figure 5. The audio-video conversion radio frequency box RF-H is to convert the AV audio and video signal output from the set-top box to the H or U frequency band of the TV, and its working voltage is 5V, which is output by the power converter to the 7805 voltage regulator integrated circuit. The device adds an amplifier circuit at the output end, which can cooperate with the traditional CATv cable TV distributor to transmit to multiple TV sets for reception. Closed circuit transmission can ensure the clarity of the image.

When in use, place the set-top box accessory device receiving and converting part on the top of the set-top box, and align the infrared emitting part with the infrared receiving window of the set-top box. As shown in Figure 6, you can receive the control signal from the wireless remote control. Realize remote control and viewing. If there are many rooms, sometimes you have to watch the program in the guest room, and sometimes you have to watch the program in the bedroom or study. If it is not convenient to use a remote control, just provide each TV with a modified remote control , More convenient to use. In addition, the universal set-top box / TV remote control is newly developed. It can be used with set-top boxes that have not yet been standardized in various regions of the country. It can also remotely control the power switch, volume and AV status of all TV sets. In this way, all viewing functions can be realized on one remote control. As mentioned at the beginning of this article: It seems that the set-top box has been installed in every room, on every TV, and it is equally convenient to watch and operate in front of each TV.

Voltage range of the AC power supply is: 100~240V

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Certificate/Conformity to standards:IEC/IECEX/CE/ROSH/IP68/ISO/EX 

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