VCS are designed to have no single point of failure and can be installed to have back up power supplies if required. This should eliminate any chance of a complete system failure. However, if in the highly unlikely event that they do then the radios, which are deemed to be safety critical, can be accessed from the front panel by a microphone for the transmitter and a radio speaker on the receiver. A desk mount “fallback” radio can also be provided for an emergency spare. A dedicated telephone line could also installed directly for emergency communications if deemed necessary.