Section II. FUNCTIONAL OPERATION OF ELECTRONIC CIRCUITS

TM 5-6350-262-14/4

Section II. FUNCTIONAL OPERATION OF ELECTRONIC CIRCUITS

5-4. General

This section identifies MWS electronic circuit elements that perform the functions described in paragraphs 52

and 5-3. The information in this section is referenced in figure 5-2 (electronic schematic diagram)

In figure 52, operational alarm signal flow is from left to right. The loop sensor wire monitor signal generator

and buffer elements occupy the lower left half of the diagram. The interconnection interface with the J-SIIDS Control

Unit is located at the extreme right. The color of each SPU internal hookup wire insulation is stated in parentheses.

Numbers in circles identify PWB Assembly screw terminals. Numbers enclosed by stars indicate circuit juncturers where

signal characteristics may be measured with a standard oscilloscope.

Note

Under controlled laboratory or shop conditions, the star--enclosed locations could be considered

test points TP? Test values at these points could be considered performance standards But,

since military arms rooms may not satisfy EMI test conditions, the test information given later in

table 5.1 must be treated as informative only. rather than procedural.

5-5. Operational Alarm Circuitry

a. Signal Flow. Low frequency signals, measured in manovolts, are induced in the loop sensor wire by removal of a

weapon from its rack. These signals are fed into the SPU through the EMI-shielded input and filter assembly. They then

pass through the signal injection transformer, Tl, and on to the primary of the step-up transformer, T2. From the

secondary of T2, the signals are amplified (times 114 at 0.5 Hz) by the low-noise bandpass preamplifier, U1. The output

of the preamplifier (U1 pin 6) is low-pass filtered, buffered, and amplified (times 520 at 0.6 Hz) by the bandpass post-

amplifier, U2. The output of the postamplifier (U2 pin 6) enters the bipolar signal level detector (U3 and U4 and

associated circuitry) Plus and minus -levels are established by fixed resistors R9 through R12. Sensitivity is adjusted by

variable resistor R35 in series with fixed resistor R13. The outputs of the bipolar signal level detector (U3 pin 6 and U4

pin 6) are OR'd by diodes CR5 and CR6, and transistor Q1. The output of Q1 triggers the alarm one-shot (1/2 of U5).

The output of the one-shot turns on the operational alarm relay drivers, Q4 and Q6. This operates (opens) the

operational alarm output relay, K1. When K1i contacts open, the impedance across the output terminals (1) and (2)

changes from less than 2K to more than 100K Ohm.

b. Signal Characteristics. If a general purpose oscilloscope is used to measure the operational alarm signal

characteristics, the approximate values listed in table 5-1 should be obtained.

5-6. Tamper Alarm Circuitry

a. Signal Flow. A 1 KHz line monitoring signal is generated by a square wave oscillator (1/2 of U5S This signal

(output U5 pin 11) is applied to the primary of the step-down balanced injection bridge transformer, T1, through a buffer

network (Q8 and Q91 When the loop sensor wire is intact and operational (neither open nor shorted), T1 is balanced by a

reference load, R20, in the SPU, and the network L4 and R33 in the EOL Module. If the loop sensor wire is cut or

shorted, T1 becomes unbalanced, and an output appears at the base of the tamper detector, Q3. Rectified and filtered

by the tamper detector, the signal switches on relay drives Q5 and Q7. This operates (opens) the tamper alarm output

relay, K2. When K2 contacts open, the impedance across the output terminals (5) and (6) changes from less than 2K to

more than 100K Ohm.

b. Signal Characteristics. If a general purpose oscilloscope is used to measure the tamper alarm signal

characteristics, the approximate values listed in table 5-1 should be obtained.

5-3