Different types of stereo minijacks

Just the other day, as a matter of fact, about two weeks ago, I was at a client’s place and was trying to solve an issue with connecting a Polycom voice-conferencing unit with her laptop. The input of the aux port on the Polycom used a mini TRS jack. We wanted to connect it to the laptop she was using. So we tried and found out that that it did not work. It is only when I trawled the Internet for information when I came across this drawing above. Now I know where I went wrong. Not all jacks are wired up the same…there are differences.

The standard TRS (tip, ring sleeve) jack can be used to refer to an unbalanced stereo or balanced mono. But if the jack is a small 3.5mm TRS jack, it normally is for unbalanced stereo. However, look at the TRRS (tip, ring, ring, sleeve) jacks on the right of the photo. They are not alike. Trust Apple to come up with another format. So whenever possible, quiz the vendor that supplied the equipment with a TRRS jack and ask them what the contacts of the TRRS jack are connected to.

Another thing to bear in mind about these different TRRS connectors is whether they conform to CTIA (Cellular Telecommunications Industry Association) or the older OMTP (Open Mobile Terminal Platform). The older OMTP is like the Nokia headset connector. The CTIA is like the Apple connector on the right. So for TRS 3.5mm jacks to be compatible with TRRS, the second ring in the TRRS socket needs to be the return to ground. No wonder I have no issues with my wife’s iPad when I connect my TRS output to it!