Abstract: A test circuit includes a first test circuit. The first test circuit includes a first light-emitting diode (LED) and a first resistor. An anode of the first LED is connected to a power supply. A cathode of the first LED is connected to a collector of a bipolar junction transistor (BJT) through the first resistor. An emitter of the BJT is grounded. A base of the BJT is connected to the power supply. A type of the BJT can be determined according to status of the first LED.

Abstract: An electrical connector includes an enclosure, a male member, a female member, and an operating member. The enclosure defines an opening in an end thereof. The female member is slidably mounted in the enclosure, and includes a housing defining a plurality of through holes. The male member is fixed in the enclosure, and includes a plurality of pins passing through the through holes of the housing respectively. The operating member is connectable to the female member to be controlled to make the housing of the female member move out of the opening of the enclosure to allow the electrical connector to act as a female type connector; or to make the housing to be retracted in the enclosure, such that the pins extend out of the through holes of the housing to allow the electrical connector to act as a male type connector.