GPIB Switches Information
GPIB switches enable several GPIB controllers to share one or more GPIB devices, or they allow a single GPIB controller to operate multiple GPIB bus systems. Users of up to four computers can share a single GPIB device such as a printer or plotter. GPIB switches may also be used to select various peripherals independently. Using GPIB switches is a very cost-effective way for several users to maximize the potential of a GPIB peripheral device. GPIB switches may be used as bus switches, or as multiplexers. If used as a bus switch, the device allows a GPIB controller, connected to the common port, select and control devices attached to the other ports. If used as a multiplexer, device allows the bus controller connected to the general ports to share the common bus and any devices connected to it.
GPIB switches use one of three common technologies to carry on their basic functions (although there are specialized varieties, such as optical switches, available as well). The three common switch types are relay switches, solid-state switches and radio frequency (RF) switches.
Relay switches use a mechanical relay to rout or switch signals. They are used to switch or to scan high voltage signals. There are three types: armature, dry-reed, and mercury-wetted switches. The relay type can be: SPST (single-pole (1-wire) , single-throw), SPDT (single-pole (1-wire), double-throw), or DPDT (double-pole (2-wire), double-throw).
Solid-state switches use transistors (FETs and others) to route or switch signals. They are used in applications that require high-speed scanning of low-level signals (±10 V). Because they do not have any moving part these switches have a very long life.
RF switches are ideal for routing high-frequency signals.
The General Purpose Interface Bus (GPIB) protocol, also known as IEEE 488 or HPIB (Hewlett-Packard Interface Bus), was designed to connect computers and peripherals to share data and control information from many sources. Hewlett-Packard developed this bus and called it HPIB. Later it was defined in the IEEE 488 Standards. Every GPIB network must have a GPIB adaptor card. Up to fourteen devices can be connected to each GPIB adaptor.