Digital Regenerator 1A12A8-continued

TM 11-5820-695-35

difference (subtraction) will yield a "clean" orderwire

positive (C48) peak levels of the composite

signal. However, using just the filtered data only signal

data/orderwire signal. The voltage at the junction of

as the second input to the subtractor is not sufficient to

R49 and R50 is the algebraic sum of the voltages across

assure a "clean" orderwire signal, because the from

capacitors C47/C48. The input at U9-6 is adjusted

radio signal may vary in amplitude. To compensate for

(R40) for a maximum peak-to-peak level of 4 volts at

this variable, an automatic gain servo loop is used to

U9-11. The corresponding average value at the junction

generate the second input to the subtractor. In the

of R49 and R50 is 2.6 volts (max.). This signal is

servo loop, the LF data signal is analog multiplied times

applied as a reference voltage at the inverting input (pin

the orderwire plus LF data signal. In the resultant

5) of comparator/slicer U10 to set the slicing level. The

signal, the (LF data)2 component contains a positive

from radio signal (U9-11) is applied at U10-4. As the

average value that can be used as a control signal to set

signal at U10-4 varies above and below the average

the input level of the second signal at the subtractor as

(reference) signal at U10O-5, U10 slices the signal at

required. With a level-controlled input, the subtractor

data transitions and provides the balanced data signal at

output signal tracks in the proper direction to maintain

UlO-13 and -14. Center slicing between peaks of the

maximum LF data component cancellation.

from radio signal regenerates the data signal because

its amplitude is relatively large compared to the

(4) The composite data/OW signal from U9-ll

amplitude of the orderwire signal. The output signals at

is applied to a low pass filter (LPF) comprised of U4B

U10-13 and -14 are balanced to ground through

(the active element) and R36, R37, R38, C33 and C34.

resistors R58, R59, R61, and R62 and routed to module

The cutoff frequency is 22 kHz (3 dB down). The output

A5 at P1-K and -L.

at U4B-10O (LF data plus orderwire) is applied through

(3) Simple filtering is not sufficient to

C38 and R55 to subtractor U4A at pin 1. The input at

accomplish separation of the orderwire from the

U4A-2 is the filtered data only signal. Derivation of this

composite data/OW signal. This is principally because

signal is explained in (5) below. The output at U4A-12 is

the low frequency components of the data signal occupy

the difference between these two input signals (input at

the same part of the frequency spectrum as the

pin 1 minus input at pin 2).

orderwire signal.

The system used to effect the

(5) The retimed, regenerated data only signal

separation takes advantage of the fact that the data and

(from A5) is applied at U8B-3 and U8A-1. The signal

orderwire signals are independent variables and that the

from U8A-2 is passed through LPF U18B (identical to

data signal is easily regenerated (2) above). The basic

LPF U4B, (4) above) and amplified in X3 amplifier U1A.

function of the orderwire extraction process is

The signal at UlA-12, approximately fixed in level, is

accomplished in subtractor U4A. One input to U4A is

applied to analog multiplier U5. A second input to U5

the composite data/OW signal with the high frequency

(at pin 1) is supplied by the output of U4A ((4) above).

components filtered out. The other input is derived from

The signal is applied through coupling network C39/R66.

the retimed, regenerated data only signal (from A5) with

This is the orderwire signal with a residual level of the

the high frequency components filtered out by an

LF data signal. These signals are analog multiplied in

identical filter. If the two input signals to subtractor U4A

U5. The output at U5-4 is

are matched in low frequency data components, their

Change 6

2-24.13