What are Plugs & Jacks and what are they used for?

Plugs & Jacks are usually used for the transmission of line-levels (0.775 volts). Their major applications are the connections of instruments like guitars, keyboards, headphones, ...

Plugs & Jacks are used for Microphone-signals if you handle them with a patch-panel. Optionally they are also used for low power speaker applications.

There are two main groups of Plugs & Jacks:

• 2-pole connectors (TIP & SLEEVE)
• 3-pole connectors (TIP, RING & SLEEVE)

In the nonprofessional HiFi-area it's common to use the 3-pole-connector for stereo signals (headphones) and the 2-pole-connector for mono-signals.

In the professional broadcast and audio industry the 2-pole-connector is used in combination with unbalanced cables for short and interference-insensitive transmittals (guitar-cable).

For more sensitive applications like digital transmissions or longer lines it is the custom to use 3-pole-connectors together with balanced cables (to avoid EMI - electromagnetic interference), but it's still a mono-signal (balanced-mono-signal).