here is some info on the keyboard i found
Macintosh Plus Keyboard (M0110A):
Introduced and included with the Macintosh Plus in 1986, it was an extended keyboard that had a built-in numeric keypad. In 1987 it was updated to Apple's new Platinum gray color. It continued to use the telephone-cord style connector to the CPU and was interchangeable with the M0110. Though Apple switched all other keyboards to Apple Desktop Bus connectors by this time, this keyboard was manufactured unchanged for 4 more years until the Plus was discontinued in 1991.
Data port:
The Macintosh 128K, Macintosh 512K and Macintosh Plus from Apple used 4P4C connectors to connect the keyboard to the main computer housing. The connector provided power to the keyboard on the outer two conductors and received data signals on the inner pair. The cable between the computer and the keyboard was a coiled cord with an appearance very similar to a telephone handset cable.[6] The connector wiring, however, required a polarized straight through pinout. Using a telephone handset cable instead of the supplied cable could short out the +5 volt DC supply and damage the computer or the keyboard.[7]
Some consumer equipment such as DirecTV set top boxes include a 4P4C low-speed data port connector.[5] Such connectors can be adapted for use with a computer's serial port so that control commands can be sent from the computer to the set top box.
how would i go about converting the signal to usb with a teensy and is this a "AT Keyboard" ?
http://en.wikipedia.org/wiki/AT_keyboard