Phono plugs come in 3 diameters 6.3mm (l/4"), 3.5mm (1/8") and 2.5mm (1/16"). Each of the three diameters is available in mono (2-pole) and stereo (3-pole) versions. The mono version can be distinguished from the stereo by the number of insulating rings on the shaft. The stereo version has 2 insulating rings which divide the shaft into 3 poles known as the TIP, RING & SLEEVE. The mono version has one insulating ring which divides the shaft into 2 poles which are known as the TIP & RING. A mono plug in a stereo jack may damage the host device because one side of the jack is shorted on the mono shaft. A stereo plug in a mono jack will not usually cause damage, but will not function properly since only one side is connected. The Phono plug was originally known as a Phone Plug as it was developed and used by Bell Labs for telephone patch cables.
Mono Phono Plug
| Model |
A (OD) |
B (L) |
 |
| 2.5mm |
2.5 |
10-12 |
| 3.5mm |
3.5 |
10-15 |
| 6.3mm |
6.3 |
30-32 |
Stereo Phono Plug
| Model |
A (OD) |
B (L) |
 |
| 2.5mm |
2.5 |
10-15 |
| 3.5mm |
3.5 |
10-15 |
| 6.3mm |
6.3 |
30-32 |
