Auxiliary Port (AUX)

Last Updated: June 9, 2017

Definition - What does Auxiliary Port (AUX) mean?

An auxiliary port (AUX) is the logical name for a standard communications port. AUX is an asynchronous serial port with an interface that allows the auxiliary input of audio signals for:

  • MP3 players
  • Headphones
  • Portable music players
  • Amplifiers
  • Speakers

It is an interface that permits a PC or other device to transmit or receive data one bit at a time. Generally, the AUX port on a PC is computer port 1 (COM1), which is the first serial port with a preconfigured assignment for serial devices.

The AUX port is typically used for audio equipment that receives peripheral sound sources, such as digital music players or audio speakers. The peripheral sound device is connected to an AUX port or other medium such as a vehicle’s audio jack.

An auxiliary port is also known as an auxiliary jack or auxiliary input.

Techopedia explains Auxiliary Port (AUX)

Although there are no set standards specifically for the AUX port, the serial port is standardized by RS-232. The RS-232 defines:

  • Electrical features
  • Significance of each pin connector
  • Physical size of the pins
  • Timing and meaning of the signals

It outlines the function of each line and signal timing. The RS-232 standard is also known as EIA 232, EIA RS-232, and as TIA-232-F, issued in 1997. This was due to the continual advancements of technology in pin design, changes in external data storage units and higher speed communication.

System resource configurations on a PC are selected for each port and identified as COM1, COM2, COM3, COM4, etc. Each COM location has an interrupt request (IRQ) address and input/output (I/O). The IRQ address is a signal sent from a device to the central processing unit (CPU) specifying an event, such as an audio signal starting or stopping. The I/O receives and transfers data to and from a device such as an MP3 player.

Although most systems have an AUX port, some older models do not. Nonetheless, there are adapters available that allow a sound device to work through an older system.

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