HP 4278A Operation Manual page 162

Table 4-13, Typical Input Electrical Characteristics
Input Signal
START IN (Opto-Isolated}
START IN (TTL Level) 1
1 S c h m i t t -Trigger input, hysteresis = 0.8V.
2 D o n o t u s e l e s s t h a n 5 m A , opto-isaiator m u s t have 5 m A m i n i m u m f o r proper
operation.
Input Current
Low H i g
0 - 250uA 5
Input Voltage
2.0V ( Input Current= 5mA )
Input Threshold Voltage
Low
0.8V
Input Current
Low
-0.4mA
4-97
h
- 60mA
High
1.6V
High
20uA