We have always had our CCTV system fed into our cable so that regardless what room of the house you are in you can simply turn to a specific channel and see what the cameras see.
This is accomplished by taking the composite video signal from the CCTV DVR (usually a quad screen split or some such), feeding it through an agile modulator (a device that converts a signal from a composite source into a designated frequency specific to a cable television channel) which is then combined into the CATV line for the house (a notch filter is used to block a specific channel range so there is no interference on the channel used by the modulator).
1 – CATV feed from cable company.
2 – Signal is split – one line goes to cable modem to minimize drop loss.
3 – Cable signal is fed through a ‘notch filter’ which eliminates a specific cable band (channels 72-78 are deleted).
4 – Cable signal and CCTV modulated feed (set on channel 75) is combined, then fed to various locations.
Hey presto, your cameras are now easily accessible from anywhere in the house and you can check what goes ‘bump’ in the night by simply changing channels.