# Devices and Protocols

Destinations utilize devices and protocols as resources to carry out sessions.

Devices usually consist of hardware within the RTU:

- The date and time clock (TOD)
- The data/fax/voice modem
- Local serial ports
- Miscellaneous inputs and outputs.

Protocols are similar to languages. Protocols are the agreed upon languages which machines use to talk to each other. Devices can be inputs to, outputs from, or triggers for sessions with destinations.