Macintosh Keyboard

pinout

This connector is present on the Macintosh 128K, 512K, 512K enhanced, and Macintosh Plus.

4 pin RJ11 female connector  at the computer

Pin Name Dir Description 1 CGND Chassis ground 2 KBD1 ? Keyboard clock (input to VIA) 3 KBD2 ? Serial data line 4 +5V +5 VDC Note: Direction is Computer relative Keyboard.

4 pin RJ11 male connector  at the keyboard

Source:www.pinouts.ru