Busy executives and technicians can carry their own personal buzzer – rather like a pocket electric bell – to warn them which they are wanted. Doctors on their rounds in a sprawling hospital, for example, can be called to a particular ward, or firemen on routine duty to a fire alert.
The pocket alarm, known as bleeper (or beeper) because of the sound it emits, to a battery-powered miniature radio receiver turned to one station. The bleep is made by a tiny crystal that vibrates to produce sound when electric signals are passed to it. The signals are generated in the bleeper’s electronic circuits, triggered by a radio signals transmitted at the touch of a button from the control unit.
The simplest bleeper can emit several different signals, rather like the dots and dashes of Morse code. Four long bleeps, for example, could mean ‘Ring the office’, or interspersed long and short ones ‘Come to reception’. More advanced types can display short message, or can store messages.
The system is known as radio-paging. A small network can call up to about 100 receivers, either separately or simultaneously in a group. Each receiver has a number, and the controller makes contact by sending the receiver number and then the required message.
Long-range paging services are operated by commercial companies who transmit messages to their subscribers’ bleepers from a control room. The world’s largest paging network is operated by British Telecom, who have transmitters covering various zones throughout the country.
Radio-paging systems all have to be licensed, and are allocated a frequency, generally around the 27mHz waveband in Australia. The operating range varies according to the power of the transmitter but could be 100 miles (160km).
Picture Credit : Google