IBM 5150 Technical Reference page 49

Rear Panel
Pin
Signal
1 Motor Control
2 Ground
3 Motor Control
4 Data In
5 Data Out (Microphone or
Auxiliary)
Cassette
Connector
5-Pin DIN Connector
Electrical Characteristics
Common from Relay
Relay N.O. (6 Vdc at 1A)
500nA at
±
13V - at 1,000 - 2,000 Baud
250 IlA at 0.68Vdc
or **
0.075Vdc
* All voltages and currents are maximum ratings and should not be exceeded.
* * Data out can be chosen using a jumper located on the system board.
(Auxiliary --0.68 Vdc or Microphone --0.075 Vdc).
Interchange of these voltages on the cassette recorder could lead to damage
of recorder inputs.
Cassette Interface Connector Specifications
1-30 System Board