Another circuit protection from power surges/spikes application note from Littelfuse. Link here (PDF)
AC power line disturbances are the cause of many equipment failures. The damage can be as elusive as occasional data crashes or as dramatic as the destruction of a power supply, computer terminal, or television set. Power line disturbances go by many names transients, surges, spikes, glitches, etc. but regardless of the name, an understanding of their characteristics and the operation of the various protection devices available is necessary to design an effective protection circuit. This Application Note will illustrate how to design high performance, cost-effective surge protection for equipment connected to AC power lines. The role of gas discharge tube (GDT) surge arresters specifically designed for AC power line protection will also be discussed.