ACCURATE ELECTRONICS 1040120000 Посібник - Сторінка 2

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ACCURATE ELECTRONICS INC

WWW.ACCURATE.ORG

PO BOX 1654 97075-1654 8687 SW HALL BLVD 97008

3.06 The bridge may be used in tandem to increase the number of available

ports in a 4wire bridge network. This is done by connecting the input and

output of one port (usually the last) of one bridge to the input and output,

respectively, of one port (usually the first) of another bridge module. Tandem

connection of two (2) Model 10401200 Bridges, for example, provides a

4wire 10way bridge. Tandem applications are generally accommodated in the

lossless mode, as loss in this mode through all input and output port

combinations is constant at 0 dB.

3.07 The limiting factor in the number of modules that can be used in tandem

is cross-port coupling (crosstalk). The cumulative effect of cross-port

coupling generally limits the number of bridge modules that can be used in

tandem to three or four.

3.08 Because these are active bridges, as opposed to more conventional

resistive bridges, the level and impedance control functions may also be

performed by a pad-transformer module, instead of by more expensive line

amplifiers. One pad/transformer is required for each input and output port

used. If more gain is required at a particular port than can be provided by the

bridge module's active circuitry, a line amplifier may be used instead of a

pad or pad/transformer module.

3.09 The 10401200 affords a choice of port-to-port insertion loss to permit

interfacing with a variety of facilities and equipment. If a carrier channel or

other standard-level 4-wire interface (+7dB receive, -16dB transmit) is

required, the total 23dB loss option is selected. When lossless bridging is

required, the 0dB option is selected. Option jumpers on each leg permit an

amount of port-to-port insertion loss to be selected: -7.0dB in receive ports

and -16dB in transmit ports, or 0dB.

4. INSTALLATION

Inspection

4.01 The bridge modules 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.

Mounting

4.02 Each module mounts in one position of the Type-10 mounting Shelf.

The module plugs physically and electrically into a 56-pin connector at the

rear of the Type-10 Shelf.

Installer Connections

4.03 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.

4.04 Attempts to troubleshoot the bridge internally is not recommended.

4.05 Figure 4 lists external connections to the module. All connections are

made via wire-wrap at the 56-pin connector at the rear of each module's

mounting shelf position. Pin numbers are found on the body of the 56-pin

connector. Bridge module pin numbers are found on the printed circuit board,

even numbers on the component side, odd numbers on opposite.

NOTE: External connections are compatible with other manufacturers.

Level Adjustments

4.06 The receive levels are adjusted so that the levels from each port at the

input bridging point are all equal. The input bridging point is accessible at the

front panel RX OUT calibration jack. The receive levels are adjusted using

the front panel RX level controls and the -7dB receive pads located on the

main board. The receive level adjustment range is -4dB to +12dB when the

receive pad is in the 0 (zero) position and -11dB to +5dB when in the -7dB

position.

4.07 Connect a terminated transmission measurement set (TMS) to the RX

OUT calibration jack. Apply a tone separately to each receive port. Adjust

the RX level controls / receive pads as required to achieve equal levels from

each port. The specific value of the bridging level is determined by each

installation. Levels in the range of -10dB to 0dB are acceptable.

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.

Practice Section 10401200 Rev A

BEAVERTON OR USA 503.641.0118

4.08 The transmit levels are set to meet the requirements of the equipment

connected at each transmit output port. The transmit levels are adjusted using

the front panel TX level controls and the -16dB transmit pads located on the

main board. The transmit level adjustment range is -6dB to +12dB when the

transmit pad is in the 0 (zero) dB position and -22dB to -4dB when in the -

16dB position.

4.09 Using a TMS inject a tone at the front panel TX IN calibration jack. The

level of the injected tone should be equal to the bridging level used above.

Adjust the TX level control / transmit pads as required to achieve the desired

level at each transmit port.

5. OPTIONS

5.01 Each line CIRCUIT of Model 10401200 contains two push-on jumper

options: one selects the -7 dB RCV PAD (CH1 to CH6 - RCV), and the other

selects the -16 dB XMT PAD (CH1 to CH6 - XMT). Locations of these

jumpers on the module's printed circuit board are shown in FIGURE 3. These

jumpers are normally set for the same amount of insertion loss, although they

may be set for different amounts if desired. Set all jumpers to the 0 position

for lossless (0dB insertion loss) bridging or set all jumpers to select 23dB

insertion loss as required for carrier-channel or other standard level (+7/-

16dB) 4-wire interfacing. After jumpers are set, further optioning or

alignment is required. (See Circuit Description 5.0)

Receive Pad Selection

5.02 The receive pad is normally selected when the Model 10401200

interfaces with a 4-wire carrier facility. The normal + 7 dBm receive level

from the carrier facility is attenuated by 7 dB, thus presenting a 0 dBm level

to the bridge.

Transmit Pad Selection

5.03 The XMT PAD is normally selected for carrier applications. The normal

0 dBm output from the bridge is attenuated by 16 dB, thus presenting a

standard - 16 dBm transmit level to the 4-wire carrier facility.

6. CIRCUIT DESCRIPTION

6.01 Model 10401200 provides summing and distribution of six VF or data

channels. This circuit description is intended to familiarize you with the 4-

wire 6-way Active Bridge modules for engineering and application purposes

only. Troubleshooting procedures should be limited to those prescribed in

Section 8 of this Practice. Please refer to the block diagrams, Figure 2 as an

aid in following the circuit description.

6.02 The Active Bridge circuitry is identical for each port of the bridge. This

circuitry consists of five-input summing circuit and, for each port output, an

integrated-circuit operational amplifier (op amp). The summing circuit

provides balanced 600 ohm terminating impedance for each input port. For a

particular output port, the summing circuit adds the transmission energy from

all other input ports (ie. all input ports except the one with the same number

as the output port) at a low-impedance summing point. The low impedance

of this summing point provides input port isolation.

6.03 The op amp provides switch-controlled gain to overcome the loss of the

summing circuit, and the 10401200 has six such networks.

6.04 References to transmit and receive are with respect to the bridge. All

transmit line and receive line circuits for each port are identical; therefore,

circuit description is based on RX Port 1 and TX Port 1.

6.05 Data or VF signals enter the Bridge on the RX Port 1 tip and ring leads

and are transformer-coupled (via T1) to the input of operational amplifier U-

1. A -7dB RX PAD can be selected to provide the proper level for 4-wire

carrier applications. The front-panel-mounted RX 1 LEVEL potentiometer,

connected in the feedback loop of U-1, provides a level of adjustment of -4

dB to + 12 dB. This is used to compensate for losses in the receive line. The

output of U-1 is coupled to the operational amplifiers associated with transmit

lines 2, 3, 4, 5, and 6 thru a summing network. Thus, all signals present at the

RX LINE 1 input appear at the TX LINE outputs of ports 2,3,4,5 and 6 but

not at the TX port of channel 1.

January 2014

FAX 503.646.3903