A device selector is a number which specifies a device. It specifies the interface select code (ISC) to which a device is connected. If more than one device can be connected to that interface (i.e., the GPIB interface), then the address of the device is appended after the ISC. It can be just a primary address or a primary address and several secondary addresses. Each address is specified with two digits; thus 1 is specified as 01. A device selector can be up to 15 digits.
Several examples follow: If a printer has a primary address of 1 and is connected to a GPIB interface with ISC 7, then the device selector for the printer is 701. If an instrument is connected to the RS-232 interface with ISC 9, then the device selector for the instrument is 9. If a GPIB plotter has a primary address of 2, a secondary address of 11 and is connected to a GPIB interface with ISC 14, then the device selector for the plotter is 140211.
