User Manual

VI-
3
The buzzer control comes from pin 5 on microcontroller U14. The control signal turns on the base of
transistor Q1, which allows current to flow through the single tone magnetic buzzer. Jumper J4 simply turns
off the buzzer.
The carrier disable circuit simply applies a shutdown voltage to the driver pallet in the system. The U14
generates the signal out of pin 21 and controls relay Q2 through R17. When Q2 is turned off, the shutdown
voltage to the driver is floating and the carrier is on. During a fault condition, when Q2 is turned on, the
shutdown voltage is applied to the carrier disable on the driver.