SWITCHBOARDS

The Truth

Telephone:

A switchboard (also called a manual exchange) was a device used to connect a group of telephones manually to one another or to an outside connection, within and between telephone exchanges or private branch exchanges (PBXs). The user was typically known as an operator. Public manual exchanges disappeared during the last half of the 20th century, leaving a few PBXs working in offices and hotels as manual branch exchanges. The electromechanical automatic telephone exchange, invented by Almon Strowger in 1888, gradually replaced manual switchboards in central telephone exchanges. Manual PBXs have also for the most part been replaced by more sophisticated devices or even personal computers, which give the operator access to an abundance of features. In modern businesses, a PBX often has an attendant console for the operator, or an auto-attendant avoiding the operator entirely.

Electric:

An electric switchboard is a device that directs electricity from one source to another. It is an assembly of panels, each of which contain switches that allow electricity to be redirected. The operator is protected from electrocution by safety switches and fuses. There can also be controls for the supply of electricity to the switchboard, coming from a generator or bank of electrical generators, especially frequency control of AC power and load sharing controls, plus gauges showing frequency and perhaps a synchroscope. The amount of power going into a switchboard must always equal to the power going out to the loads. Inside the switchboard there is a bank of busbars - generally wide strips of copper to which the switchgear is connected. These act to allow the flow of large currents through the switchboard, and are generally bare and supported by insulators. Power to a switchboard should first be isolated before a switchboard is opened for maintenance, as the bare Busbars represent a severe electrocution hazard. Working on a live switchboard is rarely necessary, and if it is done then precautions should be taken, such as standing on a thick rubber mat, the use of gloves etc.