BBC select: a terrestrial subscription television service

The service is broadcast over the BBC´s two terrestrial UHF transmitter networks, at night when the transmitters are not required for normal television. Video Crypt was chosen as the basis of the system. The service entitlements are held on a smart card. The data which is broadcast also carries service codes which tell the decoder which service is being broadcast and on which channel. The decoder can then switch to the appropriate channel, descramble the pictures and sound, and switch on the VCR