IEEE 1284 - The parallel printer interface.

IEEE 1284, the standard for bidirectional parallel printer bus support, defines two interface levels and specifies a physical and electrical interface.

The Level I interface is for devices that need reverse-mode capabilities but don’t operate at high speeds. The Level II interface is for both bidirectional and high-speed communications.

The 1284 standard also defines connectors for use in the parallel interface. The 25-pin DB25 connector is defined as the Type “A” connector. The Telco 36, a 36-conductor, 0.085" centerline Champ connector with bale locks is defined as the Type “B” connector. The Type “C” connector is a 36-contact, 0.050" centerline mini connector with clip latches.

Learn more:
IEEE 1394 - Firewire