The activation switch is essential to the set up. Detecting the actual motion of the rocket is the only reliable method to trigger the pitching cameras. Methods based on timing from igniter are grossly unreliable. However any switch located so close to the blast of the motor has to be very well constructed. Other ideas for a launch detect switch such as a pressure plate the rocket rested on were considered. In the end the idea of a rod that rested above the aft rail button was used.
The gases from the exhaust are very corrosive to electronic components not to mention the high temperatures from the blast. A very high quality seal switch is used. The switch is sealed in an aluminium enclosure and a lever arm is used to lie on top of the lower rail guide. As the rocket rises it momentarily rotates a cam on a switch to start the pitching timers. The wire used is high temperature, harsh environment wire. This method protects the switch very well from the blast of the motor.