The speech communication system transmits and receives voice communications to and from ground locations or other aircraft.

The speech communication system includes the VHF communication system, the HF communication system (option), and the satellite communication (SATCOM) system (option).

The VHF communication system supplies short range, air-to-ground, and air-to-air communications in the 118.000 MHz to 151.975 MHz band, tuned in increments of 8.33 or 25 kHz.

The HF communication system supplies long range, air-to-ground, and air-to-air voice communication in the 2.0000 to 29.9999 MHz band. The HF communication has 280,000 communication channels usually tuned in 100 Hz increments.

The SATCOM uses satellites as relay stations to transmit on long distances. SATCOM can prevent atmospheric interference which can occur when HF communications are used.

The speech communication system has interfaces with the other aircraft systems that follow:

• Audio Integrating System
• Electronic Flight-Instrument System
• Flight Management System.