| Audio signals | 0.5V RMS, <1K output impedance, >10K input impedance. |
| Red, Green, Blue | 0.7V pk-pk +/- 2dB, 75R input and output
impedance. Note that the Red connection (pin 20) can alternatively carry the S-VHS Chrominance signal, which is 0.3V. |
| Composite Video / CSync |
1V pk-pk including sync, +/- 2dB, 75R input and
output impedance. Bandwidth = 25Hz to 4.8MHz for normal TV Video de-emphasis to CCIR 405.1 (625-line TV) |
| Fast Blanking | 75R input and output impedance. This control voltage allows devices to over-ride the composite video input with RGB inputs, for example when inserting closed caption text. It is called fast because this can be done at the same speeds as other video signals, which is why it requires the same 75R impedances. 0 to 0.4V: TV is driven by the composite video input signal (pin 19). Left unconnected, it is pulled to 0V by its 75R termination. 1V to 3V: the TV is driven by the signals Red, Green, Blue and composite sync. The latter is sent to the TV on pin 19. This signal is useful when using a TV to display the RGB output of devices such as home computers with TV-compatible frame rates. Tying the signal to 5V via 100R forms a potential divider with the 75R termination, holding the signal at around 2V. Alternatively, if a TTL level (0 to 5V) negative sync pulse is available, this will be high during the display periods, so this can drive the blanking signal via a suitable resistor. |
| Control Voltage | 0 to 2V = TV, Normal. 5 to 8V = TV wide screen 9.5 to 12V = AV mode |
| Comms Data | These signals allow devices to
communicate serial data. Few devices do, so they can be ignored safely. |
| Shield | This is the overall shield of the connector case and the cable shield foil. |
The control voltages are not well documented, and some are probably reserved for future use. Try to stick to the voltages mentioned here.
See also SCART Cable and SCART Socket