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TM 55-1925-285-13&P
CHECK ALARM toggle switch A1S3 (figure 6, item 3). This switch is used to test the OCM electronics (ON, UP
position), or to operate the Ultrasonic Vibrator Assembly (UVA) continuously (DOWN position).
Processor Printed Circuit Board (PCB) (figure 6, item 4). This circuit board provides the primary control signals
for the OCM system, including all indicator panel displays. It controls the sampling sequence and solenoid
valves. It also electronically measures, stores, and compares the signals provided by the turbidimeter (part of the
SDA), and controls the range and alarm limit (ppm) of the OCM. In addition to the main indicator panel, it
provides two Light Emitting Diodes (LEDs) on the back side of the Processor PCB that are used for troubleshoot-
ing. The CHECK ALARM toggle switch A1S3 (figure 6, item 3), described in the paragraph above, is also in-
stalled on the processor PCB.
Power Printed Circuit Board (PCB) (figure 6, item 5). This circuit board provides the electrical interface points
with the other PCB's, the SDA, switch plate sub-assembly, remote indicator (alarm) assembly, and remote relay
assembly. The circuit board also distributes the 115 Vac power to the other components, produces DC power for
the other control circuit components, contains the system fuse (2 amp) providing circuit protection, contains the
main alarm limit relay, and contains the Elapsed Time Indicator (ETI).
Generator Printed Circuit Board (PCB) (figure 6, item 6). This circuit board produces a 50 kHz signal, which
drives the UVA (part of the SDA).
Noiseless Transformer (figure 6, item 7). This transformer is used to isolate and condition incoming 115 Vac
power to reduce Electromagnetic Interference (EMI) noise and susceptibility.
Noise Filter (figure 6, item 8). This filter is used to reduce electrical noise coming into and going out of the OCM
through the input power cable so that it does not electrically affect sensitive equipment, and is not affected by
other electrical equipment.
REMOTE INDICATOR (ALARM) ASSEMBLY
The cable from the sampling/sensor assembly (A1P2) connects to receptacle A2P1 (figure 7, item 1) on the
bottom of the enclosure and provides all power (120 Vac, single-phase, 60 Hz), alarm, and display signals for its
operation. The remote indicator (alarm) assembly also provides the following controls and indicators:
PUSH TO CHANGE ALARM LIMIT (PPM) pushbutton switch A2S1 (figure 7, item 2). This switch alternately
selects the OCM alarm limit (15 or 70 PPM) when pressed. This switch functions only when the system is
operated in the automatic mode (alarm limit selector switch A1S2 is in the REMOTE position). Each time the
switch is pressed, the alarm limit toggles between 15 and 70 ppm.
PUSH TO SILENCE pushbutton switch A2S2 (figure 7, item 3). This pushbutton switch alternately engages and
disengages the alarm buzzer when pressed.
The circuitry of the remote indicator (alarm) assembly includes an alarm PCB (figure 8, item 1), an audible buzzer
(figure 8, item 2), and an indicator faceplate (figure 7, item 4). The alarm PCB contains the electrical circuits,
switches A2S1 and A2S2, LED status displays, and numerical LED effluent oil content display. The audible alarm
buzzer is mounted to the back of the enclosure. It is activated when the selected alarm limit is exceeded. The
buzzer can be disengaged by the PUSH TO SILENCE pushbutton switch A2S2. The indicator faceplate provides
legends for the visual OCM status indicators and switches A2S1 and A2S2.
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