Closed-circuit radio explained

A closed-circuit radio is a radio that emits over a very small range, typically a college campus. This system can be achieved from two ways:

• By tying into the PA System^[1]
• By using existing power lines, telephones lines, pipes, etc. to transmit a carrier current^{[2] [3] [4] [5] [6] [7]}

Notes and References

1. Web site: Radio Industry: closed circuit radio station, school radio station, college dormitories . 2011-04-16 . https://web.archive.org/web/20120927045801/http://en.allexperts.com/q/Radio-Industry-2499/2008/4/closed-circuit-radio-station.htm . 2012-09-27 . dead .
2. http://afrts.dodmedia.osd.mil/heritage/first50/Chapter%205_The%20Early%20Days%20of%20Armed%20Forces%20Radio.pdf The early days of armed forces radio
3. https://patents.google.com/patent/US2996580A/en Closed-circuit communications signal distribution system
4. https://www.ingentaconnect.com/content/intellect/rj/2013/00000011/00000002/art00003 Radio behind bars – The Polish case
5. https://www.newspapers.com/clip/49788672/closed-circuit-radio-1-wikipedia/ Closed-circuit Radio Relays Game
6. https://www.newspapers.com/clip/49788831/closed-circuit-radio-2-wikipedia/ College Closed-circuit Radio Station Gets New, More Powerful Transmitter
7. https://www.newspapers.com/clip/49789188/closed-circuit-radio-3-wikipedia/ Closed-circuit Radio Network in Homes Seen