4-27. PRELIMINARY SERVICING AND ADJUSTMENT. (CONT)
Verify that red vent cover (1) on bottom of receiver-transmitter has been removed. Check that filter hood (2) on receiver
side of receiver-transmitter is open.
Two Interlock circuits within receiver-transmitter and one within each control-indicator are provided to prevent incorrect or
hazardous operation of equipment. Equipment interlocks and their functions are described below.
Each control-indicator (1) contains S607 BLOWER INTLK (2), which is activated by removal of rear cover of control-
indicator. S607 BLOWER INTLK is an Interlock switch in series with blower motor winding. When rear cover is removed
from control-indicator, phase B and phase C of primary power to blower (3) are removed and blower does not operate.
Make sure rear cover of control-indicator is firmly secured so interlock will not prevent operation of blower when power is