SCART allows a connected device to bring it in and out of "standby" mode or to switch it to the AV channel. A VCR or other playback device will optimally power on when a cassette is inserted, power on the TV (or switch it to video mode) and then start playing immediately if the cassette's write protection tab is absent. When turned off, the VCR will ask the TV to power off, which it will do if it had been powered on by the VCR's request and if it remained in video mode. Only some TVs will do this—most only implement automatic switching to and from the SCART input.