The Bosch part 1609B05214 is a genuine replacement soft start-up module designed specifically for Bosch slide mitre saws, most notably the GCM 8 SJL.This electronic control module regulates the power supplied to the motor when you first turn the machine on. It acts as a buffer, allowing the saw to slowly ramp up to full speed instead of giving a sudden, violent jerk (known as torque kickback).