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Decoder for security camera pan/tilt: As the pan/tilt power supply voltage is divided into AC decoder and DC decoder. The AC decoder provides an AC 230V or AC 24V voltage to drive the rotation of the PTZ; a DC PTZ provides a DC 12V or 24V power supply for the DC PTZ. If the PTZ is a variable speed control, the DC decoder is also required to provide 0 for the PTZ. -33 or 36V DC voltage signal to control the speed of the DC pan/tilt rotation.
According to the communication method, it is divided into a one-way communication decoder and a two-way communication decoder. The one-way communication decoder only receives the communication signal from the controller and translates it into the corresponding action voltage/current signal to drive the front-end equipment; the bidirectional communication decoder sends the communication to the controller in addition to the performance of the one-way communication decoder. Signals, so the decoder's working status can be transmitted to the controller in real time for analysis. In addition, the front-end equipment such as alarm detectors can be directly input to the decoder. The two-way communication can be used to transmit on-site alarm detection signals to reduce the use of cables. .
In accordance with the transmission of communication signals can be divided into coaxial transmission and twisted pair transmission. The general decoder supports the communication signal transmitted by the twisted pair, and some decoders also support or simultaneously support the coaxial cable transmission method, that is, the communication signal is modulated and the video signal is transmitted together at different frequencies on the same video cable. on.
The decoder's circuit is based on a single-chip microcomputer, and consists of a power circuit, a communication interface circuit, a self-check and address input circuit, an output drive circuit, and an alarm input interface.
Decoders cannot generally be used alone and need to be used with the system host.
â— The connection line between the decoder and the head and lens should not be too long, because the voltage of the control lens is about 12 volts DC. If the transmission is too far, the pressure drop will be too large, which will result in the lens not being able to control. In addition, since the multi-core control cable is more expensive than the shielded twisted pair, the cost will increase.
â— It is a good method to seal the outdoor decoder with water-proof glue at the inlet, and the operation is simple.
â— Shielded twisted-pair cable is usually used from the host to the decoder. Multiple decoders can be connected in parallel on one line. The total length is not more than 1500 meters (depending on the site conditions). If the number of decoders is too large, some auxiliary equipment needs to be added, such as adding a control code distributor or connecting a matching resistor in parallel with the last decoder (according to the manufacturer's instructions).
What is the difference between a decoder and an encoder?
Used in multimedia encoders , mainly analog video and audio signal compression data encoding file, and the encoder to convert the data encoding file to analog audio and video signal process.