An extension cable is a length of cable used to extend the reach between two devices or components, typically to connect devices that are located farther apart. Extension cables come in various types and are used in a wide range of applications, from audiovisual setups to computer networking and beyond. Here are some common features and types:

1. **Length**: Extension cables are available in different lengths to suit various needs. They can range from a few inches to several meters or even longer, depending on the application.

2. **Connectors**: Extension cables have connectors on each end that allow them to connect to the devices they are extending. The type of connectors can vary widely depending on the devices being connected. Common types include USB, HDMI, Ethernet, audio (e.g., 3.5mm, RCA), and power connectors.

3. **Construction**: Extension cables are typically made of durable materials to withstand bending, pulling, and other stresses. They may feature shielding to protect against electromagnetic interference (EMI) or radiofrequency interference (RFI), especially in applications where signal integrity is crucial.

4. **Compatibility**: It's essential to ensure that the extension cable is compatible with the devices it will be connecting. This includes matching connector types and ensuring that the cable can handle the required data or power transmission rates.

5. **Indoor/Outdoor Use**: Some extension cables are specifically designed for indoor or outdoor use. Outdoor extension cables are usually weatherproof and may have additional features such as UV resistance to withstand exposure to sunlight and moisture resistance to prevent water damage.

6. **Specialized Types**: There are also specialized extension cables designed for specific purposes. For example, extension cords are used to extend the reach of power outlets, while USB extension cables are used to extend the length of USB connections between devices.

7. **Color Coding**: In some cases, extension cables are color-coded to help users easily identify them or organize their setups. This can be particularly useful in complex setups with multiple cables.

Overall, extension cables are versatile and essential components in many electronic setups, providing flexibility and convenience by extending the reach between devices while maintaining reliable connectivity and signal integrity.