HOW TO MAKE MAXIMUM USE OF YOUR SDI SIGNAL

HOW TO MAKE MAXIMUM USE OF YOUR SDI SIGNAL

HOW TO MAKE MAXIMUM USE OF YOUR SDI CAMERA SIGNAL
A GUIDE TO CONTACT CONTROL AND TELEMETRY

By: Don McClatchie

The CCTV industry has begun to use a new type of digital High Definition camera referred to as HD CCTV that has an SDI  signal (Serial Digital Interface) output. There are multiple manufacturers of this type of digital camera and they are very price competitive with other forms of HD surveillance cameras. The big difference with these types of digital cameras are that they can use the existing coaxial cable put in place for the old analog cameras and that no network setup is required. You just power up these cameras and the digital HD video signal starts working. Unlike the IP type digital cameras these cameras cannot be hacked electronically because they are not connected to a “computer network”. This gives your customers HD camera pictures with better security.

This new SDI camera output signal allows for additional signals to be added to the data stream without interfering with the camera video. You can ad remote control and telemetry contact signals to your SDI camera signal on the same coax cable. These signals take the form of contact closures. As an example a switch closure at one end of the SDI signal path will result in a relay contact closing at the other end of the SDI signal path. With a unit at each end of the SDI cable you can transmit contact closures and have remote control of other devices or if you wish telemetry in the opposite direction. Some examples of this remote control are the opening and closing of gates for access control or returning the push of a Panic Button and any other type of contact alarm function.
Since the contact closure information travels with the SDI video, there is no need to run extra wires along with the coax cable. This is especially useful when adding motion control or door control after the cabling has been done, when it’s difficult to go back and pull more wires. You can just use the same SDI cable for all the contacts and the video picture too.

The equipment that makes command control, and telemetry possible on an SDI signal is called the SDI-CTX (Alarm Transmitter Unit) and the SDI-CRXhttps://www.fmsystems-inc.com/product/sdi-contact-link/ (Alarm Receiver Unit). One unit goes at each end of the SDI path. If you close a contact on the SDI-CTX, a relay on the SDI-CRX will close. The contacts on the receiver mirror the operation of the contacts you supply to the transmitter. Each SDI-CTX is capable of sending eight separate control contacts per unit. If a power failure should occur the units will pass the SDI video signal. If the communication path between the transmitter and receiver is lost the receiver will hold all the contact positions and operate a special contact alarm monitor to alert you of the path loss. This equipment is available with build to order supervised alarm contact resistance if required. Please specify the contact resistance when you place your order.