Edited by hard at Jan 28, 2016 03:48 |
Recently , I used the 4-line earphones to connect Banana Pro's AV port, then heard a burst of other sounds, after some discussion, let us find the reason, come and go!
It is well known that the Banana Pro's AV port can output audio signal, but in fact the AV port also output video signal, which is a composite audio and video signal output interface, there are four level interface, please see below.So if we use the TRS earphones, we won't have to worry about the question. The definition of the TRS terminal, which includes the left channel and the right channel and the ground from top to bottom, that is to say if you put the 3-line TRS terminal interface to Banana Pro's AV port, that is absolutely no noise (I have tried), because the video signal interface and the grounding interface are combined together in 3-line TRS earphone. SO, you will suddenly understand why 3-line TRS headset compatible with any intelligent mobile phone, and sometimes you use the 4-line TRRS earphones may not be able to use it on your mobile phone!
In fact, there are two kinds of interface definition standards of the 4-line TRRS earphones,OMTP and CTIA, OMTP is commonly known as the national standard, CTIA is the international standard.
Theoretically speaking, if we use the OMTP standard earphones to connect the Pro's AV port,we should not hear the noise, because the video signal is connected to the microphone interface of the earphone, so the circuit should not be affected.
But if you use the CTIA standard earphones, because the video signal is directly connected to the grounding end of earphones, the circuit signals will be affected, so this time you will hear a burst of sound in earphones.
The main difference between these two standards is that different definitions of microphone interfaces and ground interfaces. There are many adapter cable for conversion between the two standards.
In short words, Pro's AV port is designed to output a composite video signal, allowing users easy to use RCA interface display, so you should use a 3-line TRS earphone or AV cable(as follows) to connect to it.
Banana Pro Video Plug cable 2 in 1