I’ve posted this sort of picture before, it’s what my brother refers to as the “crap on a board” image. This time I’ve taken a second to mark some of the components so I can explain what is taking place in the “crap on a board” picture.
1. RF Modulator – This device takes a composite signal (such as that spit out by your DVD player or Gaming System) and converts it into a specific frequency range which corresponds with an accepted North American television channel.
2. The Composite signal feed. In this case it is the feed from the amplified output from the CCTV system Multiplexer.
3. The new modulated signal is sent back out on the frequency given to channel 75.
4. The Modulated signal is fed into a splitter turned backwards (now acting as a combiner).
5. Unmodified CATV signal is fed through a high/low pass filter which blocks the frequency range assigned to channels 71-78 (leaving them blank – any TV viewing this feed would see nothing but snow on these channels). When the “filtered” CATV feed is combined with the modulated feed a NEW channel 75 is inserted into the CATV signal.
6. CATV Amplifier – Simply takes the new feed and increases the gain somewhat ensuring that the various sets in the house (three different runs) have clear picture.
The end result? Switch on any television in the house and switch to channel 75 and you’ll see the perimeter of the house, nicely labeled and time stamped. There remains room in the 71-78 channel range to insert two more custom channels (anything could be added here).
Not bad, total cost of the modulator/filter/amplifier arrangement? Not counting the cost of the piece of wood approximately $90 CDN.
Pretty slick, huh?