communication system used in an aircarft?

Question

types of communication system eg passenger announcement system, signs used in aircraft etc

Answer 1

Rather vague question.....

Passenger announcement system is just a standard intercom system with wires to and from microphones.

Pilot to outside communication is done using VHF frequencies on the AM waveband. There is also the ACARS system which is digital on the same waveband. That only carries digital information.

Millitary aircraft can generally use both VHF and UHF frequencies.