A multi family building owner wants the tenant to be able to see who is at the front door though their TV. The cable company can do this on the TV end. Has anyone done this. What equiment did you use? Analog or digital?
Complicating the issue is that there 4 entrances that serve 4 or 6 apartments each.

Channel Plus #5445 coupled with their DA-550BID will do this for you. You can "create" four private TV channels, one for each camera input. These really work well for this application. Take a look here:

http://www.amazon.com/s/ref=bl_sr_e...cs&field-brandtextbin=Channel%20Plus

For analog, the modulator system could work if done properly, however analog channel space for 4-6 channels may not be available in your system.

For digital, one product that may work for you is this product.

Application notes for this unit.

I would recommend that you work with your cable provider to set either system up properly.