LBI-39055
15
These terminals are not polarity sensitive. Load resistors
are not required for unused speaker outputs.
TABLE 8 −− SPEAKER CONNECTIONS
SPEAKER AUDIO PA
BOARD
TERMINAL
BLOCK
LABELING
SCREW
TER-
MINALS
Select #1 * SPKR A upper two
Unselect #1 #1 * SPKR B lower two
Unselect #2 #2 * SPKR A upper two
Unselect #3 #2 * SPKR B lower two
* Audio PA Board #1 is the board in the slot adjacent to the
Audio Matrix Board. Audio PA Board #2 is the board in the
far right-hand slot as viewed from the back of the Audio
Tower.
CAUTION !
THE SPEAKER LEADS CANNOT BE
CONNECTED TO GROUND. Connecting a
speaker lead to ground will short-circuit the
speaker power amplifier and reduce output power
considerably. Speaker damage may also occur.
These terminals are intentionally not labeled with
polarity to help prevent any of the terminals from
being connected to ground or to another amplifier.

Recorder Outputs (if used)

To provide call-check recorder support, select and
unselect audio outputs are available from the Audio Tower.
These 600-ohm outputs appear at the top terminal block on
the I/O Board. Unselect audio appears on the two terminals
labeled "UNSELECT RECORDER" and select audio
appears on the two terminals labeled "SELECT
RECORDER". Interconnect the outputs to call-check
recorders as required. These outputs are not isolated from
ground through isolation transformers and the two ground
terminals are common. See the specifications page in LBI-
39062 for audio signal output level specifications.
Figure 10 −− I/O Board Recorder Terminal Block
Pin-Out

Pager Input (if used)

Pager connections are also located on a terminal block
on the I/O Board. A 600-ohm audio input and a PTT (page
enable) input are included. The terminals are labeled
"PAGE INPUT" and "PAGE PTT" respectively.
Pager audio on "PAGE INPUT" is switched in when
"PAGE PTT" becomes active. "PAGE PTT" is active
when its two terminals are shorted together by a relay
contact (or equivalent) in the pager. During a page, no
other audio signals are applied to the Line A output. Also,
the paging signal is sent to the headsets and speakers
approximately 16 dB lower than other audio signal levels.
Connect the pager to the terminal block in accordance
with the manufacturer's instructions. As shown in Figure
11, the two (2) upper terminals on the terminal block are
the "PAGE INPUT" connections and the two lower
terminals are the "PAGE PTT" connections. These inputs
are not isolated from ground and the ground terminals are
common. See the specifications page in LBI-39062 for
audio signal input level specifications.
Figure 11 −− I/O Board Pager Terminal Block Pin-Out

Relay Outputs (if used)

Form-A relay contacts (SPST normally-open) are
available from the Audio Tower for external device control.
All relay contact connections are made at the screw-
terminal type terminal blocks on the I/O Board and Audio
UNSELECTRECORDERSELECTRECORDER
UNSELECT
AUDIO OUTPUT
UNSELECT
AUDIO GROUND
SELECT AUDIO
GROUND
SELECT AUDIO
OUTPUT
(TOP)
PAGEINPUTPAGEPTT
PAGER AUDIO
INPUT
PAGER AUDIO
GROUND
PAGER PTT
GROUND
PAGER PTT
INPUT
(TOP)