HP 61010A Owner's Manual page 45

HC244
Figure 4-4. Output Data Bits and Output Control Signals
When open collector logic levels are required, you must
provide an external pull-up resistor as well as an external
supply voltage (see Figure 4-5). If your open collector
output is connected to a device such as a relay coil, you
must include a protection diode to prevent damage to the
output stage due to voltage overshoot.
[cAirnoN
External bias voltages are limited to 12 volts.
+ 5V
+ 12V
Figure 4-S. External Connections for Open Collector Outputs
Front Panel Connections 4-5