dead-man switch   

This device is intended to act as an interlock system to prevent the driver from driving off without a tiller operator in the tiller seat. The dead-man switch is generally a foot operated pedal that must be depressed to allow the apparatus to move. Although this switch is commonly referred to as the dead-man switch it technically does not function as one, rather more as an interlock system. A more accurate name would be "transmission activation switch". (Click to enlarge)

Another type of interlock system that prevents the driver from leaving without the tiller operator requires the weight of the tiller operator in the tiller seat to activate the transmission. 

function

The driver cannot shift the transmission into drive/reverse until the tiller operator has activated the foot pedal switch. Once the apparatus is in drive/reverse the tiller operator is now able to take their foot off the pedal. Anytime the transmission is placed back into neutral it will require the tiller operator to press on the pedal to again activate the transmission. 

Some departments design their apparatus so they can not start until the tiller operator has pushed dead-man switch thus ensuring that a tiller operator is present before the apparatus is started. I DO NOT RECOMMEND this configuration for the following reasons:

• There are times when the driver is the only one at the apparatus and may need to start the apparatus:
  • When an alarm comes in and the driver wants to start the apparatus as the crew is making their way to the rig. In cold weather the driver wants to start the apparatus to get it warmed up.
  • The driver wants to start the apparatus to turn on the generator for scene lights. 
  • The driver needs to move the apparatus at an emergency scene a couple feet. For example, the driver comes back to the apparatus at a medical call while the crew is attending to a patient. The driver needs to move the apparatus a couple feet to make room for the medic rig responding in (as long as the driver verifies that the tiller wheels are in the in-line position this is possible).
  • The driver needs to set up the aerial but the rest of the crew is already engaged in other tasks. 
• All of these functions would not be possible with one person because this design requires two members to start the apparatus.