The greater the number of parallel loads, the lesser the effects of the transient. Conducted ESD normally enters a system through the touch of a fingertip or hand held metal tool. Systems which are interconnected with long wires such as telephones, oil field and automated factory instrumentation and distributed computer systems are efficient collectors of radiated lightning energy. Close proximity strikes can induce voltages of 300V or more on signal lines. Power lines running adjacent to computer data lines have been reported to induce both destructive and upsetting transient voltages.
Lines switching high current inductive loads are the most disruptive.
The exceedingly fast rise time of ESD, in the nanosecond range, produces efficient coupling into nearby wiring. A 7kV spark to a nearby metal desk was observed to upset a PC from a distance of four feet. Hard failures are those sustaining permanent damage and must be replaced to restore normal circuit operation. If some components are shorted, they may be vaporized when they become part of the driving current path. Failures resulting from latch-up often char the component and a small part of the underlying circuit board.