IEEE 488 - the general purpose interface
Also known as GPIB (General Purpose Interface Bus), IEEE-488 is the international standard for a parallel interface used for attaching sensors and programmable instruments to a computer.
When connecting IEEE-488 cables, some rules apply. The total number of devices should be 15 or less. The total length of all cables should not exceed 2 metres multiplied by the number of connected devices, up to a maximum of 20 metres. And no more than three connectors should be stacked together.
V.35 - the original serial interface