Basic Knowledge of 3.5mm Audio Interface

TS, TRS, and TRRS

The 3.5mm interface usually refers to a coaxial plug with a diameter of 3.5mm, used to connect audio devices and transmit audio signals. It consists of a tip, ring, and sleeve, and the so-called TRS or TRRS represents the number of tip ring sleeves. For example, TRS stands for a tip, a ring, and a sleeve. 

TS is the earliest mono channel, so there are only two metal pins: audio signal pin and ground pin. TRS is a stereo audio with left and right channels, which consists of three metal pins: left channel, right channel, and ground.

TRRS is an integrated headset consisting of left channel, right channel, microphone, and ground, widely used in portable devices such as mobile phones and tablets.

The definition of audio touchpoints for all TS and TRS is consistent.  
 

However, TRRS has different standards, mainly CTIA and OMTP.

CTIA and OMTP

CTIA (Cellular Telecommunications and Internet Association) is an international non-profit trade association representing the wireless communication industry. CTIA has established several standards for mobile device manufacturers to follow when designing their products. One of these standards is the CTIA headphone jack standard which defines how headphones should be connected to a mobile device.  The definitions of its TRRS four metal pins are left channel, right channel, ground, and microphone, respectively.

OMTP stands for Open Mobile Platform, which is an open-source platform developed by Nokia. It was designed to provide a universal connection between mobile phones and headsets, similar to the CTIA standard. The definitions of its TRRS four metal pins are left channel, right channel, microphone, and ground in sequence.

The CTIA standard is the more common of the two, and is used by most phone manufacturers. So, most headphone designs also use it as a standard. 
 

Though both CTIA and OMTP are used for 3.5mm jacks, there are some differences between the two standards.  Therefore, when connecting the device to headphones, please make sure to use the correct type of headphones that are compatible with the device's audio jack standard.

Swapping an OMTP headset for a CTIA one, or the other way around, will cause the sound to be either very faint or inaudible. To avoid this issue, adapters that can convert between the two types of headsets are available.

At present, the headset jack of ezcap video capture products adopts CTIA standard; If you have separate headphone and microphone on hand, you can also purchase a one to two headset adapter cable to connect your TRS headphones and microphone separately.