Equipment for transmitting video images via twisted pair.
The video signal via twisted pair is transmitted from the source, which is usually a video camera in the system, to the receiving device — this can be a monitor, digital video recorder, etc.
What does the transmitter do?
It converts the unipolar asymmetric composite video signal coming to its input into two symmetrical antiphase signals, which are transmitted via a two-wire communication line.
This is the same twisted pair.
During transmission, the video signal is weakened, and interference is superimposed on it, which can be caused by the proximity of power cables or radio-emitting devices.
Interference occurring in twisted pair wires is the same for both wires and is in phase.
A receiver is installed at the other end of the communication line, which performs the reverse conversion of the differential signal.
As a rule, a video receiver over a twisted pair is built using a differential operational amplifier, which adds the signals from two wires, amplifying the antiphase components (the gain is 50-70 dB) and suppressing the in-phase components (the suppression factor is 60-90 dB).
As a result, a standard composite signal, cleared of interference and amplified, is sent to the composite input of the receiving device.
The widespread use of this method of transmitting video signals is due to the following factors.
Firstly, it is advantageous in terms of material costs: coaxial cable is significantly more expensive.
Secondly, the use of twisted pair allows for the transmission of video from several receivers via a single multi-core cable.
The number of transmitted signals is limited only by the number of pairs of wires in the cable. Thirdly, video transmitted via twisted pair is significantly less susceptible to interference than when transmitted via coaxial cable.
It is also necessary to take into account the fact that interference arising in a coaxial cable when transmitting a video signal over long distances is often very, very difficult to compensate for without loss of quality of the useful video signal.
Passive transmitters over twisted pair (the so-called balloons) came into use when a structured cable network designed with a significant capacity reserve became the norm for equipping any office building.
The existing network is used to transmit analog video signals.
Passive devices for transmitting video over twisted pair contain only a matching transformer and do not provide the required video transmission quality and interference suppression coefficient, and are also characterized by significant attenuation of the transmitted signal.
As a rule, such devices provide video transmission without loss of quality over a distance of no more than 500–600 m. If the signal from the passive transmitter is received by an active receiver, this distance can be increased.
But these devices also have undeniable competitive advantages: they are compact and also have a low cost.
Active twisted pair transmitters are used as a deliberate design solution for transmission over distances exceeding the standard 200–300 m for coaxial cable.
Unlike coaxial cable amplifiers, such transmitters allow the use of relatively cheap twisted pair with a large cross-section (coaxial cable with a central core cross-section of 0.5 mm2 is significantly more expensive).
The differential amplifier of the active transmitter with a paraphase output must have a bipolar symmetrical power supply, which ensures the symmetry of its output signal relative to the zero point of the transmitter circuit.
The same requirement must be met for the differential amplifier of the receiver.
Otherwise, additional distortions of the transmitted signal will occur due to asymmetric leakage currents.
Nitek (USA)
The TT560 active transmitter and active receiver are designed to send data over twisted pair category 2–5 cables over distances of up to 2.2 km.
Transmission of telephone, computer and video signals, as well as data on adjacent channels, is possible over a single cable channel.
The required supply voltage is 12–24 V.
The TR515 and TR560 active receivers are used in combination with the TT560 transmitter.
The receiver's modern design, which provides protection against ground loops, background interference and noise, allows you to play video with virtually no loss of quality.
The built-in mini-switch allows you to adjust the brightness level and frequency response correction.
This provides an excellent opportunity for quick adjustment to achieve optimum image quality throughout the entire operating range, as well as for calculating the required cable length with a wide margin of safety.
This equipment functions perfectly both when upgrading existing communication and computer networks, and when creating new cable systems. The easy-to-install transmitter is resistant to voltage drops and is equipped with protection against ground loops; it is immune to noise and interference during signal transmission.
The TT560 also has a mini-switch that adjusts the brightness level and frequency response correction, so that the system remains correctly configured when using any type of cable.
Videotec (Italy)
The receiver comes with a sealed box or Euro card.
Video distribution amplifiers are available in a wide range of models depending on the consumer's choice and installation requirements.
TWM1
Miniature twisted pair transmitter. Dimensions: 40 x 25 x 63 mm. Short-circuit and surge protection.
Distance – up to 1500 m for color video signal, up to 2000 m for black and white video signal when using UTP cat. 5 cable. Power supply: 12 V + 24 V, AC/DC, max. 2 W.
TWRR1
19” rack-mountable twisted pair video signal receiver. The TWR version with a European standard board is designed for professional use with the wiring reduced to the minimum required length, for operation with a large number of receivers.
Up to 1500 m for color signal, up to 2000 m for black and white video signal when using UTP cat. 5 cable. Short circuit and surge protection.
NVT (USA)
NV-1672
The 16-channel active receiver and video signal amplifier-distributor NV-1672 provides data transmission at a distance of up to 1600 m via twisted pair of categories 2 and 3 and up to 2400 m via twisted pair of category 5.
The gain control system constantly monitors the transmitted signal and, if necessary, automatically adjusts it to the required level.
In addition, the NV-1672 has the ability to adjust the brightness and contrast for each of the 16 channels, built-in lightning protection and galvanic isolation. The device is equipped with 4 RJ-45 connectors, which provide connection of 16 channels of incoming video (4 channels for each) and 16 x 2 BNC outputs.
When mounted in a 19” rack, the NV-1672 takes up 1 slot.
NV-813SThe compact passive transceiver NV-813S allows retransmission in real time of 8 channels of color or black and white video at a distance of up to 225 m when working with a passive receiver and up to 1000 m with an active receiver. Like all NVT equipment,
The transmitter is equipped with built-in lightning protection and galvanic isolation. The device is ideal for large developing video surveillance systems, where the number of ports and cameras is constantly increasing. When mounted in a 19” rack, the NV-813S takes up 1 slot.
SEBOKS (Russia)
Passive transmitters SU-B and receivers DU-B Video signal transmission range via cable type TPP 2 x 0.5 150 m at a resolution of 500 TVL, 200 m at 400 TVL; with lightning protection option SU-BG, DU-BG – 100 m and 150 m respectively.
Active transmitters SU-1P and receivers DU-1P Are the basic ones in the group of long-range active devices; implemented on a board.
Video signal transmission range is 1200 m with a resolution of at least 500 TVL, 1500 m with 400 TVL; with the lightning protection option SU-1PG, DU-1PG — 900 m and 1200 m, respectively.
The products have lightning protection options (G), galvanic isolation (I); design: on the board (P), in a heat-shrinkable tube (T), on a BNC connector (P), in a case, including outdoor (U). Power supply — 12 V, 220 V 50 Hz (C) or on request.
Security Master
SM-201T/R
Single-channel passive video signal receiver/transmitter. Video signal transmission at a distance of up to 600 m (with any passive receiver) and up to 1200 m (with an active receiver). It is possible to install the device in a thermal casing together with a video camera. Does not require power supply. Has good noise immunity.
Built-in lightning protection and galvanic isolation. Lifetime warranty provided.
SM-301T
Single-channel active video signal transmitter.
Transmission of video signal with an active receiver over a distance of up to 1600 m (2.3 category twisted pair) and up to 2400 m (5 category twisted pair). It is possible to install the device in a thermal housing together with a video camera.
SM-301R
Single-channel active video signal receiver.
Range with a passive transmitter up to 1000 m and with an active transmitter up to 2400 m (5th category twisted pair).
Special video project (Russia)
SVP-03-T-M/SVP-04-R-M
The kit consists of the SVP-03-T-M transmitter and the SVP-04-R-M receiver, which provide a differential (symmetrical) system for transmitting a video signal in real time from the sensor (video camera) to the consumer (monitor, switch, tape recorder, etc.)
This system has high noise immunity when transmitting several different types of signals (video, audio, power, telephony, alarm, etc.) in one multi-pair cable.
DC supply voltage — 12 V.
Transmitter current consumption — 50 mA. Receiver current consumption — 70 mA. Frequency band — 50 Hz — 5 MHz. Frequency response unevenness — 3 dB. Operating temperature range: -30 + 50 oC.
SVP-03-T/SVP-04-R
The kit consists of the SVP-03-T transmitter and SVP-04-R receiver, which provide a differential (symmetrical) system for transmitting a video signal in real time from a sensor (video camera) to a consumer (monitor, switch, tape recorder, etc.) at a distance of up to 1500 m.
Such a system has high noise immunity when transmitting several different types of signals (video, sound, power, telephony, alarm, etc.) in one multi-pair cable.
The devices are made on integrated circuits from Analog Devices, have small dimensions, low power consumption and are equipped with lightning protection.
Supply voltage (AC or DC) – 24 V. Transmitter current consumption – 60 mA.
Receiver current consumption – 80 mA.
Frequency range: 50 Hz – 6 MHz.
Frequency response flatness – 3 dB.
Operating temperature range: -25 + 50 oC.