CAIRO, being the Communications Audio Interface for Remote Operations, is a standard connection between two-way radio transceivers and the various forms of microphone, loudspeaker, headphone or headset accessory which an operator may employ for vocal telecommunications. It allows the operator to select the most appropriate accessory for a particular communications need, and operate any available and appropriate transceiver to provide a communications service in a wide variety of circumstances.
The overall flexibility of the CAIRO scheme is achieved by the use of standard lightweight cables and inexpensive connectors to transport the essential operating signals for Speaker, Microphone and PTT in a common format. This format has been specifically engineered for long-line connections to ensure reliability in any radio installation, including those which may be hastily established at temporary locations in response to an emergency or pressing need. The radio can be installed near to a well-sited aerial, perhaps at the top of a multi-storey building, to minimise feeder losses and maximise take-off, or at a secure position inside a vehicle, even though the operator's position may be some considerable distance away, like the ground-floor or basement operations room, or in a temporary refuge with the vehicle parked outside.
The CAIRO approach to this general technique of Remote Operations also includes simple, passive outlet boxes which accept combination connections of pre-engineered operator accessories and thereby allow several operators to participate jointly in the activities of a particular station when the need arises.
The full CAIRO scheme also supports Augmented Operations by the further inclusion of a comprehensive transceiver interface option - CAIRO-8 - through which simple active modules may be plugged in to add a function or facility which is not otherwise present in the transceiver itself. Examples here include simple enhancements to basic voice operation, like end-of-over "break" tones ("roger-pips") or lock-and-key (DTMF) units, through to the more complex modules which automatically operate a speech channel for non-vocal messages; e.g. the TNC for "Packet" data communications. Taken together, Remoteand Augmented Operations account for all the usual applications of fixed-frequency, two-way radio systems which CAIROembodies, as the normal practices of efficient and reliable communications, in a single, hierarchical compatibility scheme for all items of equipment.