A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s. Similar devices include transponders, transverters and repeaters. In radio terminology, a transceiver means a unit which contains both a receiver and a transmitter. From the beginning days of radio the receiver and transmitter were separate units and remained so until around 1920. Amateur radio or "ham" radio operators can build their own equipment and it is now easier to design and build a simple unit containing both of the functions: transmitting and receiving. Almost all modern amateur radio equipment is now a transceiver but there is an active market for pure radio receivers, mainly for shortwave listening (SWL) operators. An example of a transceiver would be a walkie-talkie or a CB radio.
Historically, transceiver was used to interface computers to peripherals such as modems, printers, keyboards, joysticks, and a mouse. Most of these applications have now converted to other communication protocols such as the universal serial bus (USB).
Today, transceiver is used in applications such as GPS, POS, glucose meters, barcode scanners, automotive telematics, set-top boxes, gaming, and many others that require low-cost, low-speed (sub 1Mbps) serial communication.
Transceivers can handle analog or digital signals, and in some cases, both. In regions where digital coverage is spotty, a transceiver may be equipped for analog to ensure that there will be no loss of signal. The ability to receive both can drive up the cost of the transceiver, due to the need to bundle in additional circuitry. However, mixed analog/digital devices can be extremely useful for people who cannot rely on digital coverage, especially in regions with a digital cliff, an abrupt drop of digital signals which can be quite a nuisance for people using mobile devices.
ZigBee is an IEEE 802.15.4-based specification for a suite of high-level communication protocols used to create personal area networks with small, low-power digital radios.
The device has evolved steadily in accordance with application demands over the last 25 years. The transceivers are evidence of the important advances made in the industry. There is, moreover, no reason to assume that design enhancements will not continue. The transceivers will still be used in applications where lower cost and design simplicity are important. In future applications lower supply voltages and higher data rates will be considered for newer designs. Future integration will likely include galvanic isolation and overvoltage protection.