ACCURATE ELECTRONICS INC
Practice Section 104003C Rev A January 2014
PO BOX 1654 97075-1654 8687 SW HALL BLVD 97008 BEAVERTON OR USA 503.641.0118 FAX 503.646.3903
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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
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