Detailed Functional Description

TM 11-6625-3023-14/ET904-AA/MMA-010/E154 TS3684/TO 33A1-12-1173-1

(ionization potential) greater than the applied test voltage, the arrestor will not conduct and no current will be available to

light the lamp.

The circuitry develops a voltage of 500 VDC +5 percent for testing the bulk ESA units and 140 VDC +5 percent

for testing the coax and external (EOW and intercom protecting devices). These voltages represent the maximum

allowable threshold voltage that the devices may have, respectively, to be considered acceptable.

During all tests the current supplied to the devices is limited to a maximum of 16 milliamperes.

b. Detailed Functional Description. The line voltage of 115 VAC (nominal) is stepped-up by transformer T1

and rectified by diodes D1 and D2, which, in conjunction with capacitors C1 and C2, form a voltage doubler.

Approximately 760 VDC (no load) is developed across R1.

During testing (momentary toggle switches S2 and S3 depressed), approximately 15 milliamperes DC flows

through R2 or R2 and R3, depending on the position of the device selection switch, S4.

Resistor R2 in conjunction with zener diodes, D3 and D4 (acting in series), form a 500 VDC +5 percent voltage

regulator for testing the bulk ESA devices. R2 and R3 (acting in series) in conjunction with zener diode, D4, form a 140

VDC +5 percent voltage regulator for testing the coax and external (EOW and intercom protecting) devices.

Resistors R4 and R5 are current-limiting resistors employed only during the SHORT test.

Switches S2 and S3 are momentary toggle switches, both of which must be depressed to complete the current

path to the zener diodes and subsequently energize the selected output connector (either J1, J2, or J3).

Switch S4 is a rotary switch which directs the test voltage to the proper connector J1 through J3 for the particular

ESA unit to be tested.

Switch S5 places lamp L2 (R4 and R5 are used in series with L2) in parallel with the ESA device for the SHORT

test and in series with the ESA device for the OPEN test.

Switch S6 enables selection of either the TIP or RING wire of the transmission line pairs. In testing bulk units it

is only needed when checking every wire of the unit for a shorted condition (as in initial installation), since the OPEN test

on one associated wire checks the entire unit.

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