The 3.5mm or 1/8" mini "phone" plug is a tried and true connector. They are known as TS or TRS connectors. Tip Ring Sleeve denotes a stereo plug: Tip is left signal, ring is right signal, sleeve is ground. Tip Sleeve is mono: Tip is signal, sleeve is ground. Most mono jacks will accept a stereo plug no problem since the tip is always a signal. The ring either has no contact or acts as a ground in this configuration. In some instances however only a mono (Tip/Sleeve) plug will work. The 1/4" phone plugs work the same way. BTW if you want to have some fun you can pick up a 2.5mm plug and wire an old telephone handset into it and plug it into your cell phone. The best are those old AT&T black handsets. I get the greatest double takes on the street with mine.
