TECHNICAL PRINCIPLES OF OPERATION-continued

TM 11-6625-3056-12

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TECHNICAL PRINCIPLES OF OPERATION (cont)

In the TS-3981 the pattern repeats ever 32,767 bits (LONG position of PATTERN switch) or every 15 bits (SHORT

position). A SINGLE ERROR pushbutton introduces a single error in the output data pattern each time it is

pressed.

Error

A second PR Generator is used in the receiver. It is identical to the one used in the transmitter

Detection

and its output is applied to one input of the Error Detector. The second input is the data from the

path under test via the receiver input circuits. A circuit in the detector compares the data it is

supposed to have (from the second PR Generator) to that which it is actually receiving from the

input circuits. Any difference is an error.

In the ERRORS position of the DISPLAY SELECT switch, the errors are counted by, and

indicated on, the 4-digit display. This display can be reset to zero by the RESET pushbutton.

Sync Time

When the DISPLAY SELECT switch is set to SYNC TIME, the display measures the time, in

milliseconds, required for the path to acquire synchronization. This time is determined by first

setting the DATA switch to OFF which resets the Sync Time Measure circuit. The DATA switch is

then set to ON, which enables the Sync Time Measure circuit and allows 1 kHz (1 millisecond)

pulses to be counted by the display.

When the path acquires synchronization it produces a data output, which is detected by the

receiver and applied (via the Diphase-to-Binary circuit) to the Sync Time Measure circuit. This

stops the Sync Time Measure circuit and stops the 1 kHz pulses from being applied to the display.

The display reading at the time it was stopped is the number of 1 kHz pulses it counted (i.e., time

in milliseconds).

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