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An auxiliary port (AUX) is a type of standard communications port on a device that accommodates audio signals for:
If you plug speakers or mics or headsets into a primary device, with the possible exception of some types of USB setups, you’re typically connecting in through what you would call an auxiliary port.
Computer port 1 (COM1) on a traditional PC is typically configured as an audio aux port. which is the first serial port with a preconfigured assignment for serial devices.
An RS-232 standardization applies to various PC audio attachments, many of which are converted to the 3.5mm or “1/8 inch” standard audio jack on a lot of peripheral hardware.
Generally, the use of these audio ports requires different types of adapters and fittings for backward compatibility as system components evolve from many different manufacturers.
Here’s more on how this type of system worked on traditional PC platforms: the general design involved system resource configurations on a PC where engineering selected these for each port, i.e.: COM1, COM2, COM3, COM4, etc.
Each COM location had 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.
More recently, auxiliary ports and auxiliary jacks became important for the widespread distribution of digital music, through home or car speakers, or directly from a device. So the auxiliary jack and its corresponding port became extremely useful to users.
That is particularly true in the smartphone world, where the single auxiliary jack provides for so many different uses, for example, watching movies or television programming with high-quality audio direct to your headphones, playing music through headphones, participating in conference calls through a headset, etc.
With that in mind, one of the most significant pivotal changes in Apple’s smartphone design philosophy occurred when Apple took the conventional auxiliary port away from newer iPhone models.
This required the purchase of specialized headsets and other gear that plug in through the lightning port. While defended vehemently by Apple, the move was unpopular with a wide range of users, and remains an example of unanticipated interface problems that are created by the manufacturer.
Generally speaking, now that many standard auxiliary reports are becoming obsolete, companies are finding ways to make new systems backward-compatible to older devices, or in other words, to adapt older devices to play music.
New smartphone models have a universal audio port design, at least, they did until the idea of Lightning-port-audio came along.
Now, the debate around audio connectivity is a major interest in the mobile device world. Increasingly, wireless design is making the auxiliary port obsolete.
Another design principle is the “build in” of input devices and peripherals into primary devices. Examples include the shift from USB-connected webcams to cameras built into laptops, and the move from traditional mouse designs to trackpads and touchscreen interfaces.
Now, we use auxiliary ports less, because there are fewer peripheral devices to connect them to.
All of this prefigures a new set of interface paradigms that will continue to evolve in the smartphone era, where the auxiliary port is much less of a presence than it used to be.