ACCURATE ELECTRONICS 104003C User manual

Page 1 of 10
Model 104003C
January 2014
This document contains proprietary information and is supplied for identification, maintenance, engineering evaluation or inspection purposes only and shall not be duplicated or disclosed without written
permission of: ACCURATE ELECTRONICS INC By accepting this document the recipient agrees to make every effort to prevent unauthorized use of this information.
Prac_104003C0_RevA.pdf
Contents:
Section 1. General 1
Section 2. Application 1
Section 3. Installation 2
Section 4. Circuit Description 6
Section 5. Mechanical Outline 6
Section 6. Specifications 6
Section 7. Testing and Troubleshooting 7
Section 8. Maintenance 7
Section 9. Warranty 7
Section 10. Condensed Alignment Procedures 8
Figure 1. Circuit Description 10
Figure 2. (see Figure 5.)
Figure 3. Hypothetical Circuit Employing 104003C
Line Amplifiers 2
Figure 4. 4Wire Circuit Employing DX signaling 2
Figure 5. Module Switch Locations 4
Figure 6. Preliminary Alignment Procedure –
No Equalization 8
Figure 7. Final Alignment Verification –
No Equalization 8
Figure 8. Preliminary Alignment Procedure –
with Equalization 8
Figure 9. Final Alignment Procedure –
with Equalization 9
Table 1. Installer Connections to 104003C 3
Table 2. Transmit and Receive Channel
Equalized Gain Optioning 3
Table 3. Loopback Frequency Selection 4
Table 4. Loopback Level Selection 4
Table 5. Test Procedure 10
1. GENERAL
1.01 The Accurate 104003C Line Amplifier with Loopback module provides
switch-selectable level control, equalization, and impedance matching in
both the transmit and receive channels of a 4wire voice-frequency
transmission facility. Additionally, the 104003C provides tone-activated or
dc-activated equal-level loopback of the facility.
1.02 The 104003C’s transmit and receive amplifiers in the 104003C may be
individually switch-optioned to provide up to 24dB of either flat gain or flat
loss in 0.1dB increments. Maximum output level of each channel is +7dBm,
with less than 1% distortion.
1.03 Equalization in both the transmit and receive channels may be
prescription-set to introduce up to 7.75dB of slope equalization from 1000 to
3000Hz in 0.25dB increments. The module’s equalized gain adjustments are
designed to provide frequency response within + 1dB over the 300 to 3000Hz
range when used on nonloaded cable facilities.
1.04 The 104003C may be switched-optioned to match 1200, 600, or 150-
ohm impedances at both the facility and terminal ports. Transformers
associated with each of the portsare center-tapped to derive balanced simplex
leads that provide for DX, loopback, and other signaling schemes that require
a dc path.
1.05 The 104003C provides loopback toward the facility for remote testing
of the circuit. Loopback may be tone or dc activated. In the tone-activated
mode, 1 of 11 loopback-activation frequencies may be switch-selected;
loopback is released in response to the reapplication of loopback tone (two-
tone-burst operation). Loopback levels of +16dB, +9dB, -16dB, or –23dB
may be prescription-set. In the dc-activated mode, the 104003C activates
loopback for the duration of a locally applied ground signal.
1.06 Auxiliary loopback relay contacts are available at 104003C’s 56-pin
connector to light an external loopback lamp or disable an associated data set
in data applications.
1.07 The front panel of the 104003C is designed so that level adjustments
can be made while the module is mounted in place. The 104003C features a
full complement of front-panel test jacks to facilitate alignment and
maintenance activities. Both bridging and opening bantam-type jacks are
provided at each port. A red light-emitting diode (LED) on the front panel
lights when the 104003C is in the loopback mode.
1.08 The 104003C incorporates an internally regulated power supply that
permits operation on –22 to –56Vdc filtered input. Current requirements
range from 30mA in the quiescent state to 65mA with both the transmit and
receive channels at maximum output. A green LED on the front panel lights
when power is applied to the module.
1.09 Surge protection in provided for the input and the output of both the
transmit and the receive channel. Reverse-battery protection and transient-
limiting circuitry are provide in each channel’s internal power supply circuit.
1.10 As a Type-10 module, the 104003C mounts in one position of a Type-
10 Mounting or apparatus case installation. In relay rack applications, up to
12 modules may be mounted across a 19-inch rack, while up to 14 modules
may be mounted across a 23-inch rack. In either case, 6 inches of vertical
rack space is used.
2. APPLICATION
2.01 The 104003C Line Amplifier with Loopback is designed for use on
4wire voice-frequency transmission facilities, where it provides bi-
directional level control, amplitude equalization, and impedance matching.
In addition, the module’s tone or dc-activated loopback circuitry allows
remote testing of the facility. Thus, the 104003C is equivalent to a 4wire-to-
4wire voice-frequency repeater with loopback. The 104003C may be used
as either a terminal or an intermediate repeater. Figure 3 shows a hypothetical
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Practice Section 104003C Rev A
LINE AMPLIFIER with LOOPBACK MODULE
MODEL 104003C

ACCURATE ELECTRONICS INC Practice Section 104003C Rev A January 2014
WWW.ACCURATE.ORG PO BOX 1654 97075-1654 8687 SW HALL BLVD 97008 BEAVERTON OR USA 503.641.0118 FAX [phone]
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2
off-premise-extension (OPX) circuit in which 104003C Line Amplifiers are
used in a variety of typical applications.
LEVELS
2.02 Levels in both the transmit and the receive channel are individually set
to provide up to 24dB of either flat gain or flat loss in 0.1dB increments.
Front panel switches allow either gain or loss to be introduced into either
channel independently. Maximum output of either channel is +7dBm, with
less than 1% distortion.
EQUALIZATION
2.03 Active slope equalization is provided in both the transmit and the
receive channel of the 104003C. Use of the module’s equalizers in one or
both channels is dependent upon the module’s position in the circuit.
Equalizing at the receive end of the circuit (post-equalization) is generally
preferable to equalizing at the transmit end (pre-equalization). Pre-
equalization tends to amplify high-frequency signals to a level that is
conducive to crosstalk. Post-equalization not only eliminates this problem
but also expedites the equalization process because the circuit is easier to
equalize at the receive end. In some applications, pre-equalization may be
necessary. Use of the 104003C as a bi-directional amplifier at an
intermediate point in a 4wire circuit, for example, often requires the use of
the transmit-channel equalizer as well as the receive-channel equalizer.
2.04 Up to 7.75dB of slope equalization (1000 to 3000hz) in 0.25dB
increments is provided in both the transmit and the receive channel to
compensate for the frequency-response characteristics of loaded and
nonloaded telephone cable. Equalized gain is independently switch-optioned
into both channels via DIP switches on the module’s front panel. The
module’s equalized gain response is designed to provide frequency response
within + 1dB over the frequency range of 300 to 3000Hz when used with any
combination of nonloaded cable. The equalized gain response is not
affected by the flat gain (or loss) adjustments, which are used to provide
precise transmission levels.
IMPEDANCE MATCHING
2.05 Impedance-matching transformers at the facility and terminal ports may
be independently switch-optioned for balanced 1200, 600, or 150-ohm
terminating impedance. This allows the 104003C to interface loaded cable
(1200 ohms),nonloaded cable(600 or 150 ohms), carrier, SX signaling units,
terminating sets, or station apparatus (600 ohms). The 150-ohm option is
primarily used to provide a small amount of equalization for short segments
of nonloaded cable.
2.06 All four impedance-matching transformers on the 104003C are center-
tapped to derive simplex leads, allowing this module to be applied to circuits
employing DX, loopback, or other dc signaling schemes (Figure 4).
LOOPBACK
2.07 The loopback feature of the 104003C allows remote testing of the levels
and frequency response of the facility. Data set disable leads (TEK5 and
TEK6) are provided to electrically disable an associated data set during
loopback. Loopback may be tone or dc activated.
2.08 In the tone-activated mode, any 1 of 11 loopback-activation frequencies
may be selected via switch option. Loopback is activated by placing the
selected loopback tone on the module’s receive pair for longer than 1.4
seconds and then removing that tone. The 1040003C initiates loopback only
upon removal of the tone and remains looped until the selected loopback tone
is reapplied to the module’s receive pair for longer than 0.7 second. The
switch-selectable loopback-tone frequency option permits up to eleven
104003C modules (when connected in a bridging arrangement) to be
individually tested from a central bridging location.
2.09 The module responds to minimum loop-back levels of –18dBm (with
receive-channel gain at zero). Gain or loss adjustments in the receive channel
will directly increase or decrease the minimum loopback sensitivity on a dB-
for-dB basis. The center-frequency stability of each loopback tone is + 0.2%;
maximum bandwidth is 75Hz. A 3dB signal-to-guard ratio and the
frequency-selection option combine to prevent inadvertent loopback.
2.10 Loopback levels of +16, +9, -16, or –23dB may be prescription-set via
two-position DIP switch S4. This option permits loopback levels to be
coordinated with various TLP’s. Standard data TLP’s (-3 receive, +13
transmit) require 16dB of gain to provide the 0dB loopback level, Federal
Aviation Agency (F.A.A) data TLP’s (-9 receive, 0 transmit) require 9dB of
gain, inverted data TLP’s (+13, receive, -3 transmit) require 16dB of loss,
and conventional voice TLP’s (+7 receive, -16 transmit) require 23dB of loss.
Once loopback levels are properly set, equal-level loopback (i.e., test tone
received equals test tone sent [+1dB], referenced to appropriate TLP’s) will
result.
2.11 In the dc-activated mode, loopback is accomplished through use of a
manually operated local key or switch or by manually applying a ground
potential to pin 1 of the 104003C’s 56-pin connector. The module remains
in loopback until the ground potential is removed.
2.12 Common pin assignments allow the 104003C to be interchanged with
other 10400X-series Line Amps or with 4412-series Data Station
Termination modules. While a 4412-series module is normally used in data
termination applications, a 104003C may, in rare cases, also be used. In data
applications, auxiliary relay contacts on the 104003C may be used to disable
an associated data set during loopback operation or to light an external
loopback lamp.
3. INSTALLATION
3.01 The 104003C Line Amplifier with Loopback should be visually
inspected upon arrival in order to find possible damage incurred during
shipment. If damage is noted, a claim should immediately be filed with the
carrier. If stored, the module should be visually inspected again prior to
installation.
FIGURE 4. 4Wire Circuit Employing DX signaling
FIGURE 3. Hypothetical Circuit Employing 104003C Line Amplifiers

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3
MOUNTING
3.02 The 104003C module mounts in one position of a Type-10 Mounting
Shelf, which is available in configurations for both relay rack and apparatus
case installation. The module plugs physically and electrically into a 56-pin
connector at the rear of the Type-10 Shelf.
INSTALLER CONNECTIONS
3.03 Before making any connections to the mounting shelf, make sure that
power is off and modules are removed. Modules should be put into place
only after they are properly optioned and after wiring is completed.
3.04 Table 1 lists external connections to the 104003C module. All
connections are made via wire wrapping to the 56-pin connector at the rear
of the module’s mounting shelf position. Pin numbers are found on the body
of the connector.
Table 1. Installer Connections to 104003C
CONNECT
TO PIN
XMT TIP OUT
41
XMT OUT RING
47
XMT SIMPLEX OUT
43 and 45
RCV TIP IN
7
RCV RING IN
13
RCV SIMPLEX IN
9 and 11
XMT TIP IN
55
XMT RING IN
49
XMT SIMPLEX IN
51 and 53
RCV TIP OUT
5
RCV RING OUT
15
RCV SIMPLEX OUT
3
LOCAL LOOP (Key controlled loopback)
1
TEK5 (data set disable lead)
19
TEK6 (data set disable lead)
21
BATT (-22 to –56Vdc battery in)
35
GND (ground)
17
DSA POWER (used in 263 Data Station
Assembly packages)
37
Note: In intermediate applications where simplex (SX) signaling is used
(see center 104003C in Figure 4), strap the simplex leads as follows: RCV
SIMPLEX IN (pin 9) to RCV SIMPLEX OUT (pin 3) and XMT SIMPLEX IN
(pin 51) to XMT SIMPLEX OUT (pin 43).
OPTION SELECTION
3.05 Option switches must be set before the 104003C is placed into service.
These switches and their functions are described in paragraphs 3.6 through
3.10. Locations of these switches on the module’s front panel and printed
circuit boards are shown in Figure 5.
CHANNEL OPTIONING
3.06 Levels. The front panel Gain/Loss slide switches for the transmit and
receive channels conditions the corresponding channel amplifier to provide
either gain or loss. If gain is required, set the switch to the GAIN position. If
loss is required, set the switch to the LOSS position. The precise amount of
gain or loss is selected via the front-panel transmit level and receive level DIP
switches. The amount of gain or loss provided by each switch position
appears on the front panel of the module adjacent to each switch position (see
Figure 5). These values are additive; thus, the amount of gain or loss selected
is the sum of those switch positions set to IN.
EQUALIZATION
3.07 Two five-position DIP switches located on the front panel introduce
from 0 to 7.75dB of slope equalization in 0.25dB increments in both transmit
and receive channels. The various settings of both equalizers are shown in
Table 2.
Table 2. Transmit and Receive channel equalized gain optioning.
Switch
positions
0.25
0.5
1.0
2.0
4.0
1000Hz*
gain
(dB)
Off
Off
Off
Off
Off
-
On
Off
Off
Off
Off
0.25db
Off
On
Off
Off
Off
0.5dB
On
On
Off
Off
Off
0.75dB
Off
Off
On
Off
Off
1.0dB
On
Off
On
Off
Off
1.25dB
Off
On
On
Off
Off
1.5dB
On
On
On
Off
Off
1.75dB
Off
Off
Off
On
Off
2.0dB
On
Off
Off
On
Off
2.25dB
Off
On
Off
On
Off
2.5dB
On
On
Off
On
Off
2.75dB
Off
Off
On
On
Off
3.00dB
On
Off
On
On
Off
3.25dB
Off
On
On
On
Off
3.5dB
On
On
On
On
Off
3.75dB
Off
Off
Off
Off
On
4.00dB
On
Off
Off
Off
On
4.25dB
Off
On
Off
Off
On
4.50dB
On
On
Off
Off
On
4.75dB
Off
Off
On
Off
On
5.00dB
On
Off
On
Off
On
5.25dB
Off
On
On
Off
On
5.5dB
On
On
On
Off
On
5.75db
Off
Off
Off
On
On
6.0dB
On
Off
Off
On
On
6.25dB
Off
On
Off
On
On
6.50dB
On
On
Off
On
On
6.75dB
Off
Off
On
On
On
7.0dB
On
Off
On
On
On
7.25dB
Off
On
On
On
On
7.50dB
On
On
On
On
On
7.75dB
*3000Hz equalized gain is twice 1000Hz level shown.
IMPEDANCE MATCHING
3.08 Two slide switches located on the main pcb select the input/output
impedances of the facility port (receive in/transmit out –S2) and the terminal
port (transmit in/receive out –S4). Each port may be set to impedances of
150 ohms, 600 ohms or 1200 ohms. See Figure 5 for location of these
switches.

ACCURATE ELECTRONICS INC Practice Section 104003C Rev A January 2014
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4
TONE-LOOPBACK FREQUENCY
3.09 Tone-loopback frequency is selected by means of 10-position DIP
switch (S3) located on the 104003C’s daughter pcb. Only 1 switch position
is required to select any 1 of 11 available frequencies. The available loopback
frequencies and settings of switch S3 are summarized in Table 3.
Table 3. Loopback Frequency Selection.
FREQUENCY
(Hz)
S3 SWITCH POSITION
SET TO ON*
2813
All switch positions OFF
2713
1
2513
2
2413
3
1913
4
1813
5
1713
6
1613
7
1513
8
1413
9
1313
10
*all other S13 switch positions MUST be set to the OFF position.
LOOPBACK LEVELS
3.10 Loopback levels of +16, +9, -16, or –23dB are selected via DIP switch
S4, located on the 104003C’s daughter pcb. Loopback level options are
described in paragraph 2.10; the various settings of switch S4 are summarized
in Table 4.
Table 4. Loopback Level Selection.
Loopback Levels
Switch Positions
S4-1
S4-2
+16dB
Off
Off
+9dB
Off
On
-16dB
On
Off
-23dB
On
On
ALIGNMENT
3.11 This alignment subsection is divided into two parts: preliminary
alignment and final alignment verification. In the preliminary alignment
procedure, impedance options are selected, equalization is introduced into the
receive and the transmit channel (if required), and gain or attenuation is
introduced in both the transmit and the receive channel to match the
transmission levels specified on the circuit level record (CLR) card. In the
final alignment verification procedure, the 104003C is placed into service and
end-to-end transmission measurements are made. If the measured levels
differ from those specified on the CLR card, the front-panel TX and RX
LEVEL switches are adjusted to provide the specified levels.
Note: Two condensed preliminary alignment procedures (Figures 6 and 8)
and two condensed final alignment verification procedures (Figures 7 and
9) may be used to facilitate alignment of the 104003C module.
PRELIMINARY ALIGNMENT
3.12 Refer to the CLR card for the required facility port and terminal port
impedances. In general, the 1200-ohm option is used to interface loaded
cable, the 600-ohm option is used to interface nonloaded cable, carrier,
station apparatus, or SF signaling units, and the 150-ohm option is used to
interface short segments of nonloaded cable in applications where a small
degree of slope equalization is required. Use S2 (Main Board) to set the
facility port impedance and S4 (Main Board) to set the terminal port
impedance.
FIGURE 5. Module Switch Locations.

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5
Note: If the 3000Hz signal level is not specified on the CLR card, gain and
equalization cannot be determined at this time. Omit paragraphs 3.13
through 3.18 and proceed to paragraph 3.19. Gain and equalization will be
determined in the final alignment verification procedures, beginning with
paragraph 3.20.
RECEIVE-CHANNEL EQUALIZATION
3.13 Refer to the CLR card for the specified 1000Hz and 3000Hz receive
input signal levels. If it is desirable to flatten the frequency response of the
facility, determine the type of cable the module interfaces and proceed as
follows:
A. Loaded cable or mixed (predominately loaded) cable: If the
module interfaces loaded cable or mixed loaded and nonloaded
cable and the loaded cable section is predominant (i.e., up to 9
kilofeet of nonloaded cable), the facility can be partially equalized
with the equalized gain provided by the module. Determine the
difference (in dB) between the 1000Hz and 3000Hz signal levels.
Divide this difference by 2and, referring to table 2, set front panel
RX EQL switch for the required amount of equalized gain. If the
exact amount cannot be selected, use the nearest lower value to
avoid over-equalization. This setting flattens the response
between 1000Hzand 3000Hz by adding 1000Hz gain equal to the
amount of equalized gain selected and 3000Hz gain equal to two
times the amount of equalized gain selected. When calculating
receive-channel levels (paragraph 3.14), the amount of equalized
gain selected above must be added to the specified receive input
level to obtain an equalized receive input level.
B. Nonloaded cable: If the module interfaces nonloaded cable,
determine the difference (in dB) between the 1000Hz and 3000Hz
signal levels. Subtract 1.5dB from this difference and, referring
to table 2, set front panel RX EQL switch for the required amount
of equalized gain. If the exact amount cannot be selected, use the
nearest lower value to avoid over-equalization. This setting
flattens the response between 1000Hz and 3000Hz by adding
1000Hz gain equal to the amount of equalized gain selected and
3000Hz gain equal to two times the amount of equalized gain
selected. When calculating receive-channel levels (paragraph
3.14), the amount of equalized gain selected above must be added
to the specified receive input level to obtain an equalized receive
input level.
C. Mixed (predominantly nonloaded) cable: If the module
interfaces mixed nonloaded and loaded cable and the nonloaded
cable section is predominant (i.e., 9 kilofeet or more of nonloaded
cable), determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Subtract 2dB from this difference and,
referring to table 2, set front panel RX EQL switch for the
required amount of equalized gain. If the exact amount cannot be
selected, use the nearest lower value to avoid over-equalization.
This setting flattens the response between 1000Hz and 3000Hz by
adding 1000Hz gain equal to the amount of equalized gain
selected and 3000Hz gain equal to two times the amount of
equalized gain selected. When calculating receive-channel levels
(paragraph 3.14), the amount of equalized gain selected above
must be added to the specified receive input level to obtain and
equalized receive input level.
RECEIVE-CHANNEL LEVELS
3.14 Refer to the CLR card for the specified 1000Hz receive input and
receive output signal levels. If equalized gain was inserted in the receive
channel (paragraph 3.13), add the amount of equalized gain used to the
specified receive input level to obtain an equalized receive input level.
Calculate the difference (in dB) between the equalized receive input level (or
the specified receive input level if equalization was not used) and the
specified receive output level to determine how much gain or loss must be
added to achieve the specified receive output level.
3.15 Set front panel RX GAIN/LOSS switch to introduce either gain or loss
into the receive channel, as required. Set to the IN position the proper
combination of front-panel RX LEVEL switches that adds up to the required
amount of gain or loss.
TRANSMIT-CHANNEL EQUALIZATION
3.16 Refer to the CLR card for the specified 1000Hz and 3000Hz signal
levels at the distant (receive-channel) location. If it is desirable to flatten the
frequency response of the facility, determine the type of cable the module
interfaces and proceed as follows:
A. Loaded cable or mixed (predominately loaded) cable: If the
module interfaces loaded cable or mixed loaded and nonloaded
cable and the loaded cable section is predominant (i.e., up to 9
kilofeet of nonloaded cable), the facility can be partially equalized
with the equalized gain provided by the module. Determine the
difference (in dB) between the 1000Hz and 3000Hz signal levels.
Divide this difference by 2 and, referring to table 2, set front panel
TX EQL switch for the required amount of equalized gain. If the
exact amount cannot be selected, use the nearest lower value to
avoid over-equalization. This setting flattens the response
between 1000Hzand 3000Hz by adding 1000Hz gain equal to the
amount of equalized gain selected and 3000Hz gain equal to two
times the amount of equalized gain selected. When calculating
transmit-channels levels (paragraph 3.17) the amount of
equalized gain selected above must be added to the specified
transmit input level to obtain an equalized transmit input level.
B. Nonloaded cable: If the module interfaces nonloaded cable,
determine the difference (in dB) between the 1000Hz and 3000Hz
signal levels. Subtract 1.5dB from this difference and, referring to
table 2, set front panel TX EQL switch for the required amount of
equalized gain. If the exact amount cannot be selected, use the
nearest lower value to avoid over-equalization. This setting
flattens the response between 1000Hz and 3000Hz by adding
1000Hz gain equal to the amount of equalized gain selected and
3000Hz gain equal to two times the amount of equalized gain
selected. When calculating transmit-channel levels (paragraph
3.17), the amount of equalized gain selected above must be added
to the specified transmit input level to obtain an equalized
transmit input level.
C. Mixed (predominately nonloaded) cable: If the module
interfaces mixed nonloaded and loaded cable and the nonloaded
cable section is predominant (i.e., 9 kilofeet or more of nonloaded
cable), determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Subtract 2dB from this difference and,
referring to table 2, set front panel TX EQL switch for the required
amount of equalized gain. If the exact amount cannot be selected,
use the nearest lower value to avoid over-equalization. This
setting flattens the response between 1000Hz and 3000Hz by
adding 1000Hz gain equal to the amount of equalized gain
selected and 3000Hz gain equal to two times the amount of
equalized gain selected. When calculating transmit-channel
levels (paragraph 3.17), the amount of equalized gain selected
above must be added to the specified transmit input level to obtain
an equalized transmit input level.
TRANSMIT-CHANNEL LEVELS
3.17 Refer to the CLR card for the specified 1000Hz transmit input and
transmit output signal levels. If equalized gain was inserted in the transmit
channel (paragraph 3.16), add the amount of equalized gain used to the
specified transmit input level to obtain an equalized transmit input level.
Calculate the difference (in dB) between the equalized transmit input level
(or the specified transmit input level if equalization was not used) and the
specified transmit output level to determine how much gain or loss must be
added to achieve the specified transmit output level.
3.18 Set front panel TX GAIN/LOSS switch to introduce either gain or loss
into the transmit channel, as required. Set to IN the proper combination of
front panel TX LEVEL switches that add up to the required amount of gain
or loss.

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permission of: ACCURATE ELECTRONICS INC By accepting this document the recipient agrees to make every effort to prevent unauthorized use of this information.
6
FINAL ALIGNMENT VERIFICATION
3.19 In this final alignment verification procedure, the 104003C is placed
into service, signal level measurements are taken, and the front-panel TX
LEVEL and RX LEVEL switches are reset, as required, to meet the levels
specified on the CLR card. Attenuation or gain introduced at this time does
not affect the equalization characteristics that may have been previously
introduced via the equalized gain switches. It is strongly recommended
that no 1000Hz level adjustments be attempted with the equalized gain
switches.
RECEIVE-CHANNEL
3.20 To perform the receive-channel’s final alignment verification, proceed
as follows:
Note: If receive-channel equalization is not required, request that thedistant
location only send 1000Hz tone at the specified level and omit step B.
A. Connect a properly terminated TMS (receive) to the RX IN MON
jack and insert an opening plug into the RX IN jack. Request that
the distant location send 1000Hz and 3000Hz tone at the level
specified on the CLR card. Verify that the tone is present and
record these levels.
B. If receive-channel equalization and gain were determined in the
preliminary alignment procedure (paragraphs 3.13 through 3.15),
omit this step and proceed to step C. If not, determine the type of
cable the module interfaces and, with the 1000Hz and 3000Hz
levels measured in step A, perform the equalization (if required)
and gain procedures in accordance with paragraphs 3.13 through
3.15.
C. Disconnect the TMS and remove the opening plug. Connect the
TMS (receive) to the RX OUT jack. Request that the distant
location again send 1000Hz tone at the level specified on the CLR
card.
D. Determine the difference (in dB) between the measured 1000Hz
receive output level (step C) and the receive output level specified
on the CLR. If any difference in levels exist, insert or remove
gain via the front-panel RX LEVEL switches to obtain the
specified receive output level.
E. To complete receive-channel verification, perform a frequency
run, measuring levels at appropriate intervals from 300to 3000Hz.
If the measured levels meet the desired frequency response
characteristic, the equalizer is properly set.
TRANSMIT CHANNEL
3.21 To perform the transmit-channel’s final alignment verification, proceed
as follows:
Note: If transmit-channel equalization is not required, insert 1000Hz tone
into the TX IN jack at the specified level and omit steps B and C.
A. Connect a properly terminated TMS (transmit) to the TX IN jack.
Send 1000Hz and 3000Hz tones at the specified level. Request
that personnel at the distant facility-side (receive) location
measure and record the level of each tone.
B. If transmit-channel equalization and gain were determined in the
preliminary alignment procedure (paragraphs 3.16 through 3.18),
omit this step and proceed to step C. If not, determine the type of
cable the module interfaces and, with the 1000Hz and 3000Hz
levels measured in step A, perform the equalization (if required)
and gain procedures in accordance with paragraphs 3.16 through
3.18.
C. Again send 1000Hz tone at the specified level. Request that
personnel at the distant (facility-side) receive location measure
and record the 1000Hz level.
D. Determine the difference (in dB) between the distant facility-side
(receive) location’s specified 1000Hz input level and the level
measured in step C (or step A if equalization is not required). If
any difference in levels exists, insert or remove gain via the front-
panel TX LEVEL switches to obtain the required level.
E. To complete transmit-channel verification, perform a frequency
run, measuring levels at appropriate intervals from 300 to
3000Hz. If the measured levels meet the desired frequency-
response characteristic, the equalizer is properly set.
4. CIRCUIT DESCRIPTION
4.01 This circuit description is designated to familiarize you with the
104003C Line Amplifier with Loopback module for engineering and
application purposes only. Attempts to test or troubleshoot the 104003C
internally are not recommended. Procedures for recommended testing and
troubleshooting in the field are limited to those prescribed in section 7 of this
Practice. Please refer to Figure 1 (see page 10) of this Practice, as an aid in
following the circuit description.
4.02 The power supply in the 104003C is a simple series voltage regulator
that uses a zener diode as a reference source. A series diode in the negative
input lead protects the circuit against reversed input power connections, and
a transorb between input battery and ground limits high-level supply transient
to a safe level.
4.03 The transmit and receive sections of the 104003C are identical. Input
and output transformers are used to interface external circuits. These
transformers also derive simplex leads at all four ports (transmit and receive,
input and output). A secondary winding of each transformer is connected to
the channel amplifier.
4.04 Clamping diodes limit the amplifiers’ input and output voltages to
internal power potentials and provide surge protection at each of the four
ports. Each channel’s amplifier section is controlled by an option switch that
introduces either negative feedback to provide loss or positive feedback to
provide gain. The precise amount of gain or loss selected is via the front-
panel TX and RX level switches. The output of each channel amplifier also
feeds a series connected equalized-gain amplifier that provides up to 7.75dB
of slope equalization via DIP switches on the module’s front panel.
TONE-ACTIVATED LOOPBACK
4.05 The input for tone-activated loopback is obtained from the output of the
receive equalizer. The tone is detected by a 2813Hz filter circuit, preceded
by a limiter for signal-to-guard control. The output of the 2813Hz filter, at
resonance, starts the 1.4-second timing cycle. The logic circuitry determines
the status of the LB relay and sets the timer for 1.4 seconds if the LB relay is
released. The LB relay remains activated until a second loopback tone is
placed on the modules’receive pair for longer than 0.7 second.
LOCAL DC LOOPBACK
4.06 Local application of a ground potential to pin 1 operates relay LB
directly, resulting in the activation of loopback. The LB relay will remain
operated (looped) until the ground potential is manually removed from pin 1.
LOOPBACK LEVEL
4.07 A prescription-set amplifier/attenuator circuit is located in the loopback
path between the receive and transmit channels. This circuit provides for the
adjustable +16dB, +9dB, -16dB or –23dB loopback level.
5. MECHANICAL OUTLINE
5.01 See FIGURE 2.
6. SPECIFICATIONS
6.01 Electrical
Note: Transmit-channel and receive-channel specifications are identical.
Facility/Terminal Port Impedances:
Switchable 1200, 600, or 150 ohms, balanced
Flat Gain or Loss: -24 to +24dB in 0.1dB increments, prescription-set
Via front-panel switches (gain or loss determined
by switch option)

ACCURATE ELECTRONICS INC Practice Section 104003C Rev A January 2014
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7
Deviation from Gain Setting Indicated by Front-Panel Switches:
+0.25dB maximum, re 1000Hz
Maximum Recommended Output Level:
+7dBm
Total Harmonic Distortion:
less than 1% at +7dBm output level
Equalized Gain: 0 to 7.75dB differential between 1000 and 3000Hz
levels, switch-selectable in 0.25dB increments
Frequency Response Deviation:
+1.0dB, re 1000Hz, 300 to 3000Hz
Delay Distortion: less than 125s, 300 to 3000Hz, re 1000Hz
(measured worst-case with equalization)
Crosstalk Loss (Between Channels):
85dB minimum, re 1000Hz
75dB minimum, re 3000Hz
Noise: 15dBrnC maximum at maximum gain
Crosstalk Loss (between units in adjacent, above, or below shelf slots):
90dB minimum, re 1000Hz
85dB minimum, re 3000Hz
Simplex (SX) Current:
120mA, maximum, with 5mA maximum unbalance
Tone Loopback Threshold:
-18dBm with no gain (Receive channel gain or loss
adjustments will directly increase or decrease the
minimum loopback sensitivity on a dB-for-dB basis.)
Tone Loopback Signal-To-Guard Ratio:
3dB minimum
Tone Loopback Frequency:
1 of 11 prescription set, center stabilities +0.2%,
75Hz bandwidth (see table 3)
Operating Times, Tone Loopback:
initiate: 1.4 seconds maximum,
loopback after removal of tone
release: 0.7 second maximum,
release during tone (two-tone-burst operation)
Local DC Loopback: ground to operate; 25mA current
Loopback Levels: +16dB, +9dB, -16dB or-23dB (+1dB), switchable
Input Power: -22 to-56Vdc, 65mA maximum, 25mA quiescent
6.02 Environmental
Operating Environment: 20to 130F (-7 to 54C)
Humidity: to 95% (no condensation)
6.03 Physical
Dimensions: 5.58” H x 1.42” W x 5.96” D
(14.17cmH x 3.61cmW x 15.14cmD)
Weight: 16 ounces (454 grams)
Mounting: relay rack or apparatus case via one
position of an Accurate Type-10
Mounting Shelf
7. TESTING AND TROUBLESHOOTING
7.01 The Testing Guide Checklist (Table 5.) may be used to assist in the
installation, testing or troubleshooting of the 104003C Prescription Line
Amplifier. The checklist is intended as an aid in the localization of trouble
to a specific module. If a module is suspected of being defective, a new one
should be substituted and the test conducted again. If the substitute module
operates correctly, the original module should be considered defective and
returned to Accurate for repair or replacement as directed below. We strongly
recommend that no internal (component-level) testing or repairsbe attempted
on the module. Unauthorized testing or repairs may void the module’s
warranty. Also, if the module is part of a registered system, unauthorized
repairs will result in noncompliance with Part 68 of the FCC Rules and
Regulations.
TECHNICAL ASSISTANCE
7.02 Contact Accurate Electronics, Inc. 503.641.0118, FAX: [phone];
Mail: PO Box 1654, Beaverton OR 97075-1654.
RETURN PROCEDURE (FOR REPAIR)
7.03 To return equipment for repair, first contact Accurate Electronics, Inc.
Enclose an explanation of the malfunction, your company’s name and
address, the name of a person to contact for further information, and the
purchase order number for the transaction. Accurate Electronics willinspect,
repair, and retest the equipment so that it meets its original performance
specifications and then ship the equipment back to you. If the equipment is
in warranty, no invoice will be issued.
8. MAINTENANCE
8.01 No preventive maintenance is required. General care is recommended.
9. WARRANTY
9.01 All Accurate Electronics Inc. products carry a full FIVE (5) YEAR
warranty on materials and workmanship. See WARRANTY in front of
catalog.
Note: Warranty service does not include removal of permanent customer
markings on the front panels of Accurate Electronics’ modules, although an
attempt will be made to do so. If a module must be marked defective, we
recommend that it be done on a piece of tape or on a removable stick-on
label.
9.02 If a situation arises that is not covered in the checklist, contact Accurate
Customer Service as follows (telephone number are given below):
Contact Accurate Electronic Customer Service
9.03 If a module is diagnosed a defective, follow the replacement procedure
in paragraph 9.04 when a critical service outage exists (e.g., when a system
of a critical circuit is down and no spares are available). If the situation is not
critical, follow the repair and return procedure in paragraph 9.05.
Replacement
9.04 To obtain a replacement module, notify Accurate Electronics. Be sure
to provide all relevant information, including the 104003C part number that
indicates the issue of the module in question. Upon notification, we shall
ship a replacement module to you. If the module in question is in warranty,
the replacement will be shipped at no charge. Pack the defective module in
the replacement module’s carton, sign the packing slip included with the
replacement, and enclose it with the defective module (this is your return
authorization). Affix the preaddressed label provided with the replacement
module to the carton being returned, and ship the module prepaidto Accurate
Electronics.
Repair and Return
9.05 Return the defective module, shipment prepaid, to Accurate Electronics
Inc. :
ACCURATE ELECTRONICS INC.
ATTN: REPAIR AND RETURN
8687 SW HALL BLVD. #100
BEAVERTON, OREGON 97008 USA

ACCURATE ELECTRONICS INC Practice Section 104003C Rev A January 2014
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permission of: ACCURATE ELECTRONICS INC By accepting this document the recipient agrees to make every effort to prevent unauthorized use of this information.
8
10. CONDENSED ALIGNMENT PROCEDURES
Figure 6. Preliminary alignment procedure- no
equalization
1.) Refer to the CLR card and determine the following: facility port
impedance, terminal port impedance, receive 1000Hz input and
output signal levels, and transmit 1000Hz input and output signal
levels. Once the facility levels are known, proceed to step 2 and
perform the remaining preliminary alignment steps in numeric
order. The paragraph referenced after each step contains a more
detailed explanation of that specific procedure. After completing
step 6, proceed to the final alignment verification (without
equalization) procedure (Figure 7) for instructions on making end
–to-end measurements.
2.) Set S2 (Main Board) for facility port impedance. (paragraph 3.8)
3.) Set S4 (Main Board) for terminal port impedance. (paragraph
3.8)
4.) If the specified receive input level is lower than the specified
receive output level, gain must be added. If it is higher, loss must
be added. Set front panel RX GAIN/LOSS switch to either GAIN
or LOSS, as required. To determine the required amount of gain
or loss, calculate the difference (in dB) between the specified
receive input level and the specified receive output level. Set to
IN the proper combination of front panel RX LEVEL switches
that adds up to the required amount of gain or loss. (paragraph
3.6)
5.) If the specified transmit input level is lower than the specified
transmit output level, gain must be added. If it is higher, loss must
be added. Set front panel TX GAIN/LOSS switch to either GAIN
or LOSS, as required. To determine the required amount of gain
or loss, calculate the difference (in dB) between the specified
transmit input level and the specified transmit output level. Set to
IN the proper combination of front-panel TX LEVEL switches
that adds up to the required amount of gain or loss. (paragraph
3.6)
6.) Insert the module into its mounting position, apply power, and
proceed to the final alignment verification (without equalization)
procedure (Figure 7).
Figure 7. Final alignment verification-no equalization
1.) Connect a properly terminated TMS (receive) to the RX IN MON
jack and insert an opening plug into the RX IN in jack. Request
that personnel at the distant facility-side location send 1000Hz
tone at their specified level. Verify that tone is present and at the
level specified on the CLR card. (paragraph 3.20)
2.) Disconnect the TMS and remove the opening plug. Connect the
properly terminated TMS (receive) to the RX OUT jack. Request
that personnel at the distant facility-side location again send
1000Hz tone at their specified level. Verify that tone is present
and record the level. (paragraph 3.20)
3.) Determine the difference (in dB) between the measured receive
output level (step 2) and the receive output level specified on the
CLR. If any difference in levels exists, insert or remove gain via
their front-panel RX LEVEL switches to obtain the specified
receive output level. (paragraph 3.20)
4.) Disconnect the TMS. Connect the properly terminated TMS
(receive) to the TX IN MON jack and insert an opening plug into
the TX IN jack. Request that personnel at the distant terminal-
side location send 1000Hz tone at their specified level. Verify
that tone is present and at the level specified on the CLR card.
(paragraph 3.21)
5.) Disconnect the TMS and remove the opening plug. Connect the
properly terminated TMS (receive) to the TX OUT jack. Request
that personnel at the distant terminal-side location again send
1000Hz tone at their specified level. Verify that tone is present
and record the level. (paragraph 3.21)
6.) Determine the difference (in dB) between the measured transmit
out-put level (step 5) and transmit output level specified in the
CLR. If any difference in levels exist, insert or remove gain via
the front-panel TX LEVEL switches to obtain the specified
transmit output level. (paragraph 3.21)
7.) Remove all test connection. Alignment is completed.
Figure 8. Preliminary alignment procedure –with
equalization
1.) Refer to the CLR card and determine the following: facility port
impedance, terminal port impedance, receive 1000 and 3000Hz*
input and output signal levels, transmit 1000Hz and 3000Hz*
input and output signal levels, and the distant (receive channel)
location’s receive 1000Hz and 3000Hz* input signal levels. Once
the facility levels are known, proceed to step 2 and perform the
remaining preliminary alignment steps in numeric order. The
paragraph referenced after each step contains a more detailed
explanation of that specific procedure. After completing step 8,
proceed to the final alignment verification with equalization
procedure (Figure 9) for instructions on making end-to-end
measurements.
*If the 3000Hz signal levels are not specified on the CLR,
equalization and gain (steps 4 through 7) cannot be determined at
this time. After completing step 3, omit steps 4 through 7 and
proceed to step 8. After completing step 8, proceed to Figure 9.
2.) Set S2 (Main Board) for facility port impedance. (paragraph 3.8)
3.) Set S4 Main Board) for terminal port impedance. (paragraph 3.8)
4.) If equalization is desired in the receive channel, refer to the CLR
card for the specified 1000Hz and 3000Hz receive input signal
levels. Determine the type of cable that the module interfaces,
and perform the appropriate equalization procedure, as described
below. (paragraph 3.13)
Loaded cable and predominately loaded mixed cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Divide this difference by 2 and,
referring to table 2, set front panel RX EQL switch for the
required (nearest but lower) amount of equalized gain.
Nonloaded cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Subtract 1.5dB from this difference
and, referring to table 2, set front panel RX EQL switch for
the required (nearest but lower) amount of equalized gain.
Predominately nonloaded mixed cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Subtract 2dB from this difference
and, referring to table 2, set front panel RX EQL switch for
the required (nearest but lower) amount of equalized gain.
5.) Note: The amount of equalized gain added in step 4 must be
added to the specified 1000Hz receive input signal level to obtain
an equalized receive input level.
If the equalized receive input level is lower than the specified
receive output level, gain must be added. If it is higher, loss must
be added. Set front panel RX GAIN/LOSS switch to either GAIN
or LOSS, as required. To determine the required amount of gain
or loss, calculate the difference (in dB) between the equalized

ACCURATE ELECTRONICS INC Practice Section 104003C Rev A January 2014
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9
receive input level and the specified receive output level. Set to
IN the proper combination of front-panel RX LEVEL switches
that add up to the required amount of gain or loss. (paragraphs
3.14 and 3.15)
6.) If equalization is desired in the transmit channel, refer to the CLR
card for the specified 1000Hz and 3000Hz receive input signal
levels at the distant (receive channel) location. Determine the
type of cable that the module interfaces, and perform the
appropriate equalization procedure, as described below.
(paragraph 3.16)
Loaded cable and predominately loaded mixed cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Divide this difference by 2 and,
referring to table 2, set front panel TX EQL switch for the
required (nearest but lower) amount of equalized gain.
Nonloaded cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Subtract 1.5dB from this difference
and, referring to table 2, set front panel TX EQL switch for
the required (nearest but lower) amount of equalized gain.
Predominately nonloaded mixed cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Subtract 2dB from this difference
and, referring to table 2, set front panel TX EQL switch for
the required (nearest but lower) amount of equalized gain.
7.) Note: The amount of equalized gain added in step 6 must be
added to the specified 1000Hz transmit input level to obtain an
equalized transmit input level.
If the equalized transmit input level is lower than the specified
transmit output level, gain must be added. If it is higher, loss must
be added. Set front panel TX GAIN/LOSS switch to either GAIN
or LOSS, as required. To determine the required amount of gain
or loss, calculate the difference (in dB) between the equalized
transmit input level and the specified transmit output level. Set to
IN the proper combination of front-panel TX LEVEL switches
that add up to the required amount of gain or loss. (paragraphs
3.17 and 3.18)
8.) Insert the module into its mounting, apply power, and proceed to
the final alignment (with equalization) procedure (Figure 9).
Figure 9. Final alignment procedure –with equalization
1.) Connect a properly terminated TMS (receive) to the RX IN MON
jack and insert an opening plug into the RX IN jack. Request that
personnel at the distant facility-side location send 1000Hz and
3000Hz tones at their specified level. Verify that tone is present
and record these levels. (paragraph 3.20)
2.) If receive equalization was determined in the preliminary
alignment procedure, omit this step and proceed to step 3. If not,
determine the type of cable that the module interfaces and, with
the measured levels from step 1, perform the appropriate
equalization procedure as described below. (paragraph 3.13)
Loaded cable and predominantly loaded mixed cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Divide this difference by 2 and
referring to table 2, set front panel RX EQL switch for the
required (nearest but lower) amount of equalized gain.
Nonloaded cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Subtract 1.5dB from this difference,
referring to Table 2, set front panel RX EQL switch for the
required (nearest but lower) amount of equalized gain.
Predominately nonloaded mixed cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Subtract 2dB from this difference
and, referring to table 2, set front panel RX EQL switch for
the required (nearest but lower) amount of equalized gain.
3.) Disconnect the TMS and remove the opening plug. Connect the
properly terminated TMS (receive) to the RX OUT jack. Request
that the distant location again send 1000Hz tone at their specified
level. Verify that tone is present and record the level. (paragraph
3.20)
4.) Determine the difference (in dB) between the measured 1000Hz
receive output level (step 3) and the 1000Hz output level specified
on the CLR. If any difference in levels exist, insert or remove
gain via the front-panel RX LEVEL switches to obtain the
specified receive output level. (paragraph 3.20)
5.) To complete receive-channel verification, perform a frequency
run, measuring and recording levels at appropriate intervals from
300 to 3000Hz. If the measured levels meet the desired
frequency-response characteristics, the equalizer is properly set.
6.) Disconnect the TMS. Connect the properly terminated TMS
(transmit) to the TX IN jack and send 1000Hz and 3000Hz tones
at the specified level. Request that personnel at the distant
facility-side (receive) location measure and record the level of
each tone. (paragraph 3.21)
7.) If the transmit equalization was determined in the preliminary
alignment procedure, omit this step and proceed to step 8. If not
determine the type of cable that the module interfaces and, with
the measured levels from step 6, perform the appropriate
equalization procedure as described below. (paragraph 3.16)
Loaded cable and predominately loaded mixed cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Divide this difference by 2 and,
referring to table 2, set front panel TX EQL switch for the
required (nearest but lower) amount of equalized gain.
Nonloaded cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Subtract 1.5dB from this difference
and, refereeing to table 2, set front panel TX EQL switch for
the required (nearest but lower) amount of equalized gain.
Predominately nonloaded mixed cable
Determine the difference (in dB) between the 1000Hz and
3000Hz signal levels. Subtract 2dB from this difference and
referring to table 2, set front panel TX EQL switch for the
required (nearest but lower) amount of equalized gain
8.) Again send 1000Hz tone at the specified level. Request that
personnel at the distant facility-side (receive) location measured
and recorded the 1000Hz level. (paragraph 3.21)
9.) Determine the difference (in dB) between the distant facility-side
(receive) location’s specified 1000Hz input level and the level
measured in step 8. If any differences in levels exist, insert or
remove gain via the front-panel TX LEVEL switches to obtain the
required level. (paragraph 3.21)
10.) To complete transmit-channel verification, perform a frequency
run, measuring and recording levels at appropriate intervals from
300 to 3000Hz. If the measured levels meet the desired
frequency-response characteristics, the equalizer is properly set.
11.) Remove all test connections. Alignment is completed.

ACCURATE ELECTRONICS INC Practice Section 104003C Rev A January 2014
WWW.ACCURATE.ORG PO BOX 1654 97075-1654 8687 SW HALL BLVD 97008 BEAVERTON OR USA 503.641.0118 FAX [phone]
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permission of: ACCURATE ELECTRONICS INC By accepting this document the recipient agrees to make every effort to prevent unauthorized use of this information.
10
FIGURE 1. CIRCUIT DESCRIPTION.
TABLE 5. Test Procedure.
Test
Test Procedure
Normal
results
If Normal Conditions
Are Not Met, Verify:
Receive
Level
Connect properly terminated
TMS (receive) to RX OUT jack.
Insert 1000Hz test tone at
specified level into RX IN jack.
Signal level
corresponds to gain
or loss setting.
-Power
-Wiring
-Proper impedance termination
(check for double termination)
-Impedance switches (S2 and S4) properly set
-Level/Equalizer switches (front-panel RX LEVEL and RX EQL) properly set
-Replace module and re-test
Transmit
Level
Connect properly terminated
TMS (receive) to TX OUT jack.
Insert 1000Hz test tone at
specified level into TX IN jack.
Signal level
corresponds to gain
or loss setting.
-Power
-Wiring
-Proper impedance terminations (check for double terminations)
-Impedance switches (S2 and S4) properly set.
-Level/Equalizer switches (front-panel TX Level and TX EQL) properly set
-Replace module and re-test
Tone
loopback
Connect selected loopback tone
at level indicated in CLR to RX
IN jack; after 2 seconds change
frequency to 1kHz; measure
output at TX OUT jack.
LPBK LED lights.
Measured transmit
level within +1dB of
transmit level
indicated on CLR.
-Transmit and receive levels properly aligned.
-Correct looopback tone selected at S3.
-Lower loopback tone level 10dB and retest.
-Replace module and retest
Tone
loopback
release
Change test signal to selected
loopback tone.
LPBK LED off after
approximately
1Second.
-Momentarily operate manual loopback (ground pin 1).
-Check transmit pair for shorted pairs.
-Replace module and retest.