A headphone or audio jack is a connection device originally designed for telephone services in the 1900s. The two main kinds of jacks used for headphones and other audio accessories are the 3.5mm jack and proprietary jacks.

A TRS 3.5mm audio jack is a standard device that connects headphones to an audio source like an iPod or mobile phone. The 3.5mm jack is used in most portable audio devices and other electronic gadgets such as stereos, digital cameras and DVD players. It is commonly used for microphones and to connect a wide range of equipment. Unfortunately, the more the plug is used the tip and ring wear away and produce crackling sounds when listening to music.

In contrast, some companies build proprietary jacks into their products thus requiring customers to buy their particular brand accessories. For example, Samsung uses proprietary jacks in their Smart Phones which entices customers to use Samsung head phones or to use an adapter to fit personal headphones.

For many consumers this is a big disadvantage, and there is constant pressure for companies to use audio jacks fitted to universal standards in their products. For example, consumers were disappointed when Apple revealed last year that it built a propriety “transmission” chip into iPhones. This is often described as an “Apple Tax” which permits consumers to use Apple products.
 
When purchasing a mobile phone, check to see which kind of audio jack it includes and if you need an adapter to plug in your favourite pair of headphones.