CCIR System A
CCIR System A was the 405 line analog broadcast television system broadcast in the UK and Ireland. It was discontinued in 1985.
Specifications
Some of the important specs are listed below.
A frame is the total picture. The frame rate is the number of pictures displayed in one second. But each frame is actually scanned twice interleaving odd and even lines. Each scan is known as a field (odd and even fields.) So field rate is twice the frame rate. In each frame there are 405 lines (or 202.5 lines in a field.) So line rate (line frequency) is 405 times the frame frequency or 405•25=10125 Hz.
The video bandwidth was 3.0 MHz. The video signal modulates the carrier by Amplitude Modulation. But a portion of the upper side band is suppressed. This technique is known as vestigial side band modulation (AC3). The polarity of modulation is positive, meaning that an increase in the instantaneous brightness of the video signal results in an increase in RF power and vice versa. Specifically, the sync pulses (being "blacker than black") result in minimum power (possibly zero power) from the vision transmitter.