I worked as an electrician in the field of traffic signal systems. In the city of Los Angeles there are 4500 intersections that have TS controls and use about 350,000 light bulbs(lamps). As you can guess there are a lot of failures most of witch are caused by powering on the individual lamps at full voltage. Hitting the filament with 4 amps(+/-) creates a lot of damage and is where lamps usually fail.
In the eighties we decided that the technology was advanced enough that using a "Soft Start" switch was feasible and would pay for it's self in a short period of time with lower failure rates.
Today there are about 125,000 solid state switches that are used to turn on the lights at signalized intersections in L. A. City.
Very basically what happens is that the 5vdc switch is energized and it starts applying ac voltage from 0 volts rising very rapidly to 120 volts and it starts a "0" degrees on the AC cycle. I'll be honest, I can't for the life of me remember how the decrease in failure rate using a "Soft Start" solid state switch saves in power consumption and lamp failure over the use of coil and armature relay switches.
Another bit of useless information brought to you courtesy of a stuck at home RV owner, stuck in a S&B doing Honey does and refurbishing said S&B.And you're welcome.
