A transceiver or transmitter/receiver is a device which combines transmission and reception capability on shared circuitry. There are a number of different types of transceivers designed for an assortment of uses, and the transceiver is the cornerstone of wireless communication. One common example of a transceiver is a cellular phone, which is capable of sending and receiving data, unlike a basic radio, which can only receive signals.
Transceivers can be divided into two rough categories: full and half duplex. In a full duplex transceiver, the device can transmit and receive at the same time. Cell phones are, again, an excellent example of a full duplex transceiver, as both parties can talk at once. By contrast, a half duplex transceiver silences one party while the other transmits. Many radio systems operate on a half duplex method, which is why people signal when they are going “out,” alerting the other user to the fact that the frequency is open for transmission.
Some transceivers are designed to be portable. Avalanche transceivers attached to the gear of skiers, snowshoers, and other people who engage in winter sports are an example of a portable transceiver. Others are stationary, like the large communications systems used in ships and satellites. The bonus of portability is that the transceiver is easy to handle and move as needed, but the disadvantage is that the device may be weak, with a limited range which can become problematic at times.
A number of factors can influence the utility of a transceiver, determining which frequencies it can use, and how far it can transmit. Satellites can utilize a wide range of frequencies and transmit across a very great distance, while a simple police radio may be limited to city limits. The more high powered a transceiver is, the more expensive it is, and also the larger it tends to be.
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.