In some examples, after a jack of a power supply is connected to a port of a device, a first safety chip may provide a signal that includes an amount of power sufficient to power a second safety chip located in the power supply. After receiving a message from the second safety chip, the first safety chip may send the second chip an instruction to cause relays in the power supply to transition from open to closed, causing power to be provided by the jack to the computing device. The first safety chip may repeatedly send a continue instruction requesting the second chip to keep the relays in the closed position. If the jack is disconnected from the port, the second safety chip fails to receive the continue instruction and causes the relays to transition back to the open position, stopping power from being provided by the power jack.