In the armed forces, a signaller or signaleer is a specialist soldier or seaman or airman responsible for military communications. Signallers, aka Combat Signallers or signalmen or women, are commonly employed as radio or telephone operators, relaying messages for field commanders at the front line (Army units, Ships or Aircraft), through a chain of command which includes Field headquarters and ultimately governments and non government organisations. Messages are transmitted and received via a communications infrastructure comprising fixed and mobile installations.