VIII
VIL
Input Voltage:
Input Current:
Pulse Width:
2.0V < H < 5.0V
OV < VI < 0.5V
Max. 0.1mA (@ VI u = 5.0V)
Max. -0.4mA (@ ViL = 0.4V)
Tp 100us
Figure 3-15. External Trigger Pulse
3-16. KEYBOARD LOCK-OUT
The 4278A has keyboard lock-out capability that disables all front panel operation except for
the power LINE switch, CONTRAST knob, and 'UNLOCK' softkey. This is useful when you
don't want the control settings changed, for example, if the 4278A is performing bin sorting
for a large number of capacitors.
3-17. SERVICE FUNCTIONS
The 4278A has special service functions for checking operation, troubleshooting, and per-
forming calibration. For detailed information on the service functions, refer to the 4278A's
Maintenance Manual (PN 04278-90100).
3-24
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