Quarter-inch or 3.5 mm jack connectors: TS (tip-sleeve) carries an unbalanced mono signal, while TRS (tip-ring-sleeve) carries either a balanced mono or unbalanced stereo signal.
TS and TRS are jack plug formats identified by the number of conductive sections separated by insulating rings on the plug shaft. A TS plug has two sections (tip and sleeve) and carries a single unbalanced channel. A TRS plug has three sections (tip, ring, and sleeve) and can carry either a balanced mono signal or an unbalanced stereo signal depending on the device.
Why it matters
DJ mixers commonly use TRS on booth and balanced outputs, headphone jacks use TRS for stereo, and many controllers have TS inputs for expression pedals or microphone inserts. Knowing which format a socket expects prevents signal loss, noise, or channel imbalance from using the wrong cable.
In practice
When a mixer labels an output as balanced mono, use a TRS-to-XLR cable to maintain the balanced circuit to the destination. When connecting headphones, a TRS-to-TRS cable carries stereo. Plugging an unbalanced TS into a balanced TRS output will still pass audio, but you lose the noise rejection benefit of the balanced circuit.
