Please tell me what mixer you have Keith.
TRS stands for Tip Ring Sleeve (or 'stereo' jack) In fact this connector can be used for 'balanced' signal cables AND stereo signals as Headphones.
'Stereo' and 'balanced' are NOT the same :
Stereo means two separate audio signals (L+R) thru the same cable (the cable has three wires). The tip of the connector used for the Left audio, the ring Right audio and the sleeve (body) is the common ground.
'Balanced' cables transport only one audio channel. The Tip is the POSITIVE (called HOT or +) signal wire, The Ring the NEGATIVE (called Cold, return or -) wire and the sleeve (body) is connected to the cable's shield. The shield in fact does not transport electricity (electrons) ...... the Stereo version does !
In fact it is a little confusing when people see aa headphone-connector it is STEREO, but on a balanced microphone it is MONO but balanced