This connector is present on Macintosh 128K, 512K, and 512K enhanced.
|2||+5V||+5 VDC. Dont use this one, it may be converted into output handshake in later equipment.|
|4||Tx+||Transmit Data, positive going component|
|5||Tx-||Transmit Data, negative going component|
|7||DSR/HSK||Handshake input. Signal name depends on mode: Used for Flow Control or Clock In.|
|8||Rx+||Receive Data, positive going component|
|9||Rx-||Receive Data, negative going component|
a. When connecting to an RS-232 device, use HSKi with data set ready (DSR) or other handshaking signals, depending on the device to be connected.