Incrementally-related Carriers (IRC)
Incrementally related carriers (IRC) is a system for assigning television channel numbers to bands of frequencies over a cable TV network. The IRC plan attempts to minimize distortion products by deriving all video carrier signals from a common source. The IRC system assigns channel frequencies (for the North American NTSC-M system) spaced 6 MHz apart. In an IRC (Incrementally Related Carrier) system, the VHF channels are at their off-air frequencies except for channels 5 and 6, which will be 2 MHz higher than usual.
In North American cable television the IRC frequency plan would be:
| Channel | NTSC-M standard |
IRC |
|---|---|---|
| 2 | 54-60 MHz | |
| 3 | 60-66 MHz | |
| 4 | 66-72 MHz | |
| 1 | 44-50 MHz1 | 72-78 MHz (A-8) |
| 5 | 76-82 MHz | 78-84 MHz (A-7) |
| 6 | 82-88 MHz | 84-90 MHz (A-6) |
Read more about this topic: North American Cable Television Frequencies
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