Intermec 074787-001 User Manual

The PB42 circuitry is protected from externally conducted or radiated 
noise, power surges, and electrostatic discharge (ESD). The following 
sections describe the protection circuitry from these different types of 
sources.

All externally accessible connectors must be protected from ESD at 15kV 
air discharge and 8kV contact discharge. Those connectors are P6, J7, P7, 
J3, and J2.

P6 and J7 are protected by bidirectional, TVS diodes. Although these are 
primarily designed for power surge protection, they also suppress ESD. The 
common mode choke, L1, also will suppress any current spikes associated 
with the ESD.

P7 is the battery connector. BATT-A and BATT-B are protected by TVS 
D11 through D10.

J2 and J3 have TVS diodes on each of their signal lines.

Even though the TVS diodes protect the printer from permanent damage, 
power glitches will still occur. These short power glitches can cause the 
software to not function properly. Therefore, the software watchdog timer 
must be enabled for the printer to recover from an ESD event without user 
intervention. For more information, see 

.