The +5 V pin guarantees at least 500 mA, and requires devices to use only 100 mA each. ADB also includes the PSW (Power Switch) pin which is attached directly to the power supply of the host computer. This is included to allow a keypress on the keyboard to start the machine without needing the ADB software to interpret the signal. In more modern designs, an auxiliary microcontroller is always kept running, so it is economical to use a power-up command over the standard USB channel.

The decoding transceiver