TA3 and TA4 look like the same tiny XLR until you try to mate them. One is three pins. The other is four. Grab the wrong cable and the lav is dead, the transmitter is fine, and you are the person holding both ends.
This is the short version of which mini-XLR is which, where each one shows up on set, and how to stop mixing them up. For the rest of the connector family, start with Understanding Audio Cables, Part 1.
What a TA3 cable is
A TA3 is a three-pin mini-XLR. You will see it on some lavs, headset mics, and older or smaller recorders. It carries a balanced mic or line signal, same idea as a full-size XLR, just in a connector that fits a belt pack.
What a TA4 cable is
A TA4 is a four-pin mini-XLR. Lectrosonics transmitters use it a lot. The extra pin is usually for bias power to the lav, so a TA3 lav into a TA4 jack is not “close enough.” It is a different wiring job.
How to tell them apart in a hurry
Count the pins. Three vs four is the whole tell. If the bag is dark, feel for the extra pin or check the connector stamp. Do not force a TA3 into a TA4 jack. You will bend a pin and then you have two problems.
If you are building or repairing a cable, match the transmitter’s pinout, not just the connector shape. Lectrosonics, Sennheiser, and Sony do not all wire a TA4 the same way.
What to keep in the kit
Keep one known-good TA3 and one known-good TA4 lav whip labeled on the connector, not the heat shrink you will lose. If a new lav shows up with no adapter, that is a booking question, not a set surprise.
Need a cable or a wireless kit in Dallas? See location sound rentals or ask booking.