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7.9.3
Setting Audio Communication Link Points
Line Interface Link 2 wire 4 wire (LK1) selects the type of audio connection required for
site communications.
Linking <2w> = selects Balanced two-wire communications. Note: This is the Default
setting.
Linking <4w> = selects four-wire communications. Transmit data is through the line-
transformer to a balanced two-wire and is from the normal two-wire connection pins.
One side of this can be connected to ground if required to make the circuit unbalanced.
Alternatively the un-balanced audio can come from (DB25 pin 6 audio) and (DB25 pin 19
ground). Receive audio is through the unbalanced input (DB25 pin 7 audio) and (DB25
pin 20 ground).
LEVEL POTS: These are factory set and should never need adjusting. However, on
long cable runs, an increase in levels may be used. Both pots increase with a clockwise
rotation. RV1 is receive level and RV2 is transmit level.
Pin No
6
19
7
20
22-25
9-12
Pin No.
8
3
16, 21
Rev. C
Line Interface Connector part of DB25 for the used slot.
Description
Hi-Z Unbalanced TX audio OUTPUT
Hi-Z Unbalanced TX audio GROUND
Unbalanced RX audio INPUT
Unbalanced RX audio GROUND
Balanced 2-wire line (first wire) / 4-wire TX
Balanced 2-wire line (second wire) / 4 wire TX
NOTE: For normal system installations, the two-wire line
is connected across pins 22 and 9 of the D25 connector
corresponding to the slot position of the RD 315 module.
The UNBALANCED INPUT should not be wired more than
a few meters in length and must be shielded, as it is a
high impedance input.
The preferred connection point for 4-wire TX output is
from the line transformer, pins 22,9.
Description
Receive Data (data to site)
Transmit Data (data from site)
Signal Ground
7.9-3
HMXMU001018
10/06
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