Example implementations relate to detection circuits. In one example, a detection circuit includes a power supply, a transistor coupled to the power supply, a port coupled via the transistor to the power supply, where the port is to transmit power received via the transistor from the power supply to a corresponding port included in an external device when the corresponding port is coupled to the port, and a detection circuit to detect a voltage between the port and the corresponding port when the port is coupled to the corresponding port and interrupt, via the transistor, power supplied to the port when the detected voltage satisfies a threshold voltage.