GAI-Tronics LE300-IP Page/Party Line Extender - Manual (Page 36)

Pub. 42004-488C
M ODEL LE300-IP P AGE /P ARTY
®
L INE E XTENDER P AGE 33 of 68
e:\standard ioms - current release\42004 instr. manuals\42004-488c.doc
09/14
Page Line Audio Monitoring Connections
The Model LE300-IP provides a balanced 600-ohm audio output for monitoring audio on both the local
and remote page lines. Connect any external audio input device (audio recorder, radio transmitter,
amplifier, etc.) to the audio line monitoring terminals using a twisted pair cable. The input impedance of
the audio device should be 600 ohms or greater. Terminals are located at connector P16 on the Main
PCBA and are labeled as shown in Table 30 below.
Table 30.
Terminal Designator Description
P16-1 PG MON L2 Page line monitor audio output (L2)
P16-2 − No connection
P16-3 PG MON L1 Page line monitor audio output (L1)
Verifying the Proper Line Balance Resistance
For proper Line Extender operation, the line balance resistance, for both page and party lines, should be set
close to 33 ohms. This can be done by enabling and adjusting the line balance potentiometers on the
69441-xxx terminal board using an ohmmeter.
When the line balance potentiometer is enabled, it is possible to measure the selected dc resistance
directly. One side of the ohmmeter should connect to the exposed header pin on the header used to enable
or disable the line balance potentiometer. The other side of the ohmmeter should connect to the side of the
associated 15-ohm series resistor closest to the edge of the printed circuit board. Ensure the 15-ohm
resistor is part of the measurement before adjusting the potentiometer for the correct resistance. All six
circuits are symmetric and their signals have minimal overlap. If the incorrect series resistor is chosen,
then the ohmmeter should read an open circuit.
Distributing Line Balance Resistance
As an increasing length of cable is added from the Line Extender the effects of cable resistance should be
taken into consideration. The farther a Page/Party
® station is connected to the system cable from the line
balance resistance the greater the chance deficiencies in system behavior may occur. The station farthest
away from the line balance will exhibit increased sidetone audio in the handset earpiece and will place
higher than nominal levels of audio onto the system cable. Stations receiving this audio nearby will have
louder than expected outputs. These same stations receiving audio from other stations near the line
balance resistance will have lower than expected outputs due to the line loss of the cable resistance. A
system showing these characteristics should have distributed line balancing.
For reference, if a line balance is installed at both ends of one mile of 18 gauge cable, then both line
balances should be set to nominally 46.7 ohms. The one mile of cable provides approximately 33 ohms of
resistance in each leg; the resulting series-parallel combination will result in the devices installed at both
ends seeing a line impedance of approximately 33 ohms.