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 TM 55-1905-219-14-9
4-64.1. TANK LEVEL INDICATION-RECEIVER-MAINTENANCE INSTRUCTIONS
(Continued).
(j) If an ALARM SILENCE switch on the receiver panel is pressed, the holding path for relays
K1 and K2 on power supply and master alarm modules PS( ) is interrupted. Relays K1 and K2 are thereby
deenergized. The B contact set of relay K1 then returns to its normally closed position, switching a steady-state
+28 volt dc level in place of the flashing voltage. As a result, the flashing of the alarm lamps now switches to a
steadily lighted condition. At the same time, the A and B contact sets of relay K2 transfer and open the current
paths for the audible alarm on the receiver panel and open the alarm contact closure for the remote alarm. The
high alarm lamps remain in the steadily lighted state until the condition that caused the alarm is removed.
When the alarm condition is removed, switch Q2 on the control module returns to the off state and relay K1 on
the control module is deenergized, open-circuiting the alarm lamps.
(k) The circuit configuration of the low alarm circuit, connected in the alarm circuit position is
essentially identical to the high alarm circuit with the exception of the arrangement of jumpers on the control
module. In a low-alarm circuit configuration, gate bias network R15-CRZ2 and threshold bias network RP3-
R16-R17 function as do their counterparts in the high-alarm circuit; thus threshold detector Q5 turns switch Q6
on causing relay driver Q7-Q8 to energize relay K2, when the fluid level signal exceeds a level selected by the
setting of Threshold Select potentiometer RP3. However, in the low alarm circuit, the exceeding of the
threshold level indicates a normal (not alarm) state. As a result, the fact that relay K2 is energized represents a
normal condition.
(l) If the fluid level in the tank drops below the height set by the adjustment of Threshold
Select potentiometer RP3 in the threshold bias network RP3-R16-R17, threshold detector Q5 turns switch Q6
off, interrupting the current path for relay driver Q7-Q8, and deenergizing relay K2. When relay K2 is
deenergized, the jumper arrangement at the contacts of the relay causes the production of the low alarm pulse
by differentiator R21-R22-R23-C5. The low alarm pulse then duplicates the effects of the high alarm pulse with
the exception that the LOW ALARM lamp, rather that the HIGH ALARM lamp, flashes.
(m) If CALIBRATE switch S1, a pushbutton on the control module is pressed, the full
calibrate voltage at the output of calibration network RP1-R1 on the control module is substituted for the output
of the fluid detection device(s) on the level signal line. Calibrate potentiometer RP1 in calibration network RP1-
R1 is then adjusted to produce full-scale deflection on fluid level meter M( ) as indicated above. A FLOAT
SIMULATOR potentiometer is provided on each receiver panel for checking the operation of the receiver panel
circuits and for performing adjustments of the threshold selector potentiometers in control module alarm
circuits. This potentiometer is connected to the
4-1332
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