4pin

4pin is a non-specific term used to describe electrical connectors that use four conductors. The four-pin designation is common in electronics and computing, but the physical form, electrical characteristics, and pinout vary by standard. Because different standards share the same pin count, a four-pin connector in one system will not necessarily mate with a four-pin in another without matching geometry and signals.

In personal computers and related hardware, several four-pin connectors are widely encountered. The Molex four-pin peripheral power connector (LP4) delivers power to older hard drives and optical drives, carrying +12 V on the yellow wire and +5 V on the red wire with two grounds. The ATX12V four-pin connector (P4) provides additional +12 V power to the CPU. The four-pin fan connector uses ground, +12 V, a tachometer signal, and a PWM control line to regulate fan speed.

Outside computing, four-pin connectors appear in other contexts as well. A common four-pin trailer connector provides lighting circuits such as left and right turn signals, tail lights, and ground. In electronics hobby and manufacturing, four-pin JST- or similar-family connectors are used for small-scale signal and power connections, including battery balance leads and LED strips.

Because many four-pin formats exist with differing footprints, correct matching of pinout, pitch, and locking mechanism is essential to ensure proper mating and function.