Electronics are used trackside for a variety of monitoring, control and communication functions. Long wires carrying the AC power necessary for the electronics to do its job can also conduct utility line disturbances (due to nearby switching, phase imbalances and load changes) into the power supply inputs. The modem telephone line intended for communicating status can allow transients cross coupled from power lines to enter the equipment shack. Both of these and control loop or sensing wiring can also act like antennas, picking up electromagnetic transients from a nearby lightning strike. Such a transient can travel down the wiring to equipment inputs, where its current, voltage and energy can easily overpower circuits not designed to handle them resulting in equipment disruption, damage or destruction. Overvoltage protectors designed to withstand and reduce transients to tolerable levels can be placed between the equipment and the incoming wiring to protect susceptable circuits.
Plug in protectors allow for quick change out if the protector is sacrificed to a particularly intense transient. Plug in protectors in the BPE8WSC resist being backed out of their connectors by severe vibration due to the compressible foam strips in the cover. In applications not requiring quick change capability, free standing protectors such as the TEL50C or E or the 420LCX or 420LEXX provide a compact, cost effective solution for up to four lines or two loops. Custom low voltage protectors working in conjunction with equalizers can protect circuits monitoring track sensors.
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