Video Security Basics

Splitting/Amplifying the Video Signal

Keep in mind the video signal used in CCTV equipment is nominally a one volt peak-to-peak signal and is impedance sensitive to 75 ohms for ideal video reproduction at the monitor. If these parameters are not kept, then the video will degrade.

Distribution Amplification
If the installation of a system requires viewing the video at multiple locations from a single camera, there are a few different ways of accomplishing this. One way is through using a distribution amplifier. This device basically takes the single video signal and reproduces the exact signal into multiple outputs; and in the case of the Pelco DA104DT you would get four identical outputs.

So, if the input signal is a one volt peak-to-peak signal you will get four output signals of the same amplitude. Providing the run distance for the type of coax used is kept within the specified length, no other equipment will be needed to reproduce a nice clear video display on each monitor. Another timesaving feature of the Pelco DA104DT is that there are not adjustments required. Just connect the unit, turn it on, and the installation is complete. If the need arises where more than four signals are required, multiple units can be linked together by simply using one of the output signals as an input signal to the next unit, and so on.

Equalizing Amplification
Due to the many factors that can effect the video signal, it is sometimes necessary to enhance the video signal (as in transmitting a nominal video signal level) directly out of the camera, through RG59 coax to a monitor, while still producing a clear video display across the entire length of the coax. In this case the coax should not exceed 750 feet (228 m).

However, let's say you need to use RG59 because it's more flexible and much easier to work with but the cable length must be 1,500 feet (457 m). The signal at this point is going to be weak and will display a very degraded picture on the monitor. As mentioned, there are many things that can effect signal strength before the signal reaches the monitor. If you find a weak signal, simply pass the weak signal through an equalizing amplifier, make the required adjustments, and once again there will be a good, strong signal that will produce a nice picture.

The Pelco model EA2010 is a post-equalizing amplifier which simply means that this device will be located close to the monitor. There's an advantage to this design in that AC power is usually more readily available at the monitoring location than it is somewhere back up the coax line, and with this type of design it only requires one person to view the monitor display while at the same time making the required adjustments to obtain the nominal signal level.

As mentioned in the example on RG59,the signal strength is good up to nominally 750 feet (228 m). With the Pelco EA2010 amplifying the signal, the same grade of coax can be used in runs of up to 3,000 feet (914 m).

In regard to any equalizing amplification system, there is another type of post-equalizing amplifier that Pelco offers. It is the half-duplex post-equalizing amplifier. This device (as far as the amplification of the video signal is concerned) is exactly like the EA2010.The difference is that the EA2000 was designed specifically for use with any of the Pelco Coaxitron® (up-the-coax) control/transmitter systems. This device enables the video signal requiring amplification to be transmitted over the same coaxial cable over which the control signal is transmitted, whereas if you used the EA2010 it would block the Coaxitron® control signal from being transmitted.