Specifications

LBI-39100
11
Assemblies inside the case include the I/O Backplane
Board mounted on the rear panel, the power supply unit
mounted to the bottom of the case, and the Audio System
Board. With the top cover removed, the Audio System
Board slides into and out of the case between two (2) plastic
printed circuit board guides attached to the left and right
inner sides of the case. When fully-inserted, rectangular
96-pin DIN-type connectors on the Audio System Board
mate with 96-pin DIN connectors on the I/O Backplane
Board.
All cable interconnections to and from external
equipment are made via connectors at the Enhanced Audio
Enclosure's rear panel. Openings in the rear panel expose the
I/O Backplane Board's connectors so they may be mated
with connectors on the cables to and from external
equipment. For example, the desk mic's cable is equipped
with a male DB-9 connector which mates with a female
DB-9 connector labeled "DESK MIC" at the Enhanced
Audio Enclosure's rear panel. This female DB-9 connector is
J5 on the I/O Backplane Board.
As previously mentioned, the Enhanced Audio
Enclosure may be rack mounted in a standard 19-inch
cabinet or case. An optional rack-mount kit is required.
When rack-mounted, the Enhanced Audio Enclosure
occupies two (2) vertical rack units or 3.5 inches.
Power Supply
As shown in the assembly diagram (page 16), the power
supply is mounted to the bottom of the Enhanced Audio
Enclosure's case. It converts ac line power (nominal 115
Vac or 230 Vac, 50/60 Hz) to regulated 12 Vdc power for
use by the Audio System Board and the attached Speaker
Assemblies. The supply is not a field-serviceable unit.
The ac on/off power switch is located on the Enhanced
Audio Enclosure's rear panel just above the detachable
IEC-320 type ac power cord connector. As viewed from the
back of the case, this switch and connector are located on
the left-hand side of the Enhanced Audio Enclosure's rear
panel.
A two-wire power cable between the power supply and
the I/O Backplane Board delivers twelve-volts dc (12 Vdc)
power to the I/O Backplane. The I/O Backplane Board
distributes this dc power to the Audio System Board via the
96-pin DIN interconnections and to its four (4) DB-9
speaker connectors at the Enhanced Audio Enclosure's rear
panel. Consequently, the power supply unit within the
Enhanced Audio Enclosure supplies dc operating power to
Speaker Assemblies connected to the Enhanced Audio
Enclosure. As described later in this manual and in
LBI-39104, this dc power is utilized by the audio power
amplification circuitry within the Speaker Assembly.
I/O Backplane Board
Inside the Enhanced Audio Enclosure, the I/O
Backplane Board is vertically-mounted on the enclosure's
rear panel. This board is the junction point for all audio
interconnections into and out of the Enhanced Audio
Enclosure to and from external audio devices. Microphones,
headsets, speakers, CEC/IMC audio lines, etc., all terminate
at the I/O Backplane Board. In addition other
interconnections made at the I/O Backplane Board include
control-type connections such as the PC's serial control data
link, the Dispatch Keyboard serial link and interconnections
to Call Director telephone equipment.
The I/O Backplane Board consists of twenty-one (21)
connectors, nineteen (19) of which extend through Enhanced
Audio Enclosure's rear panel for external device
connections. Of the three (3) internal connectors, two
directly mate with the Audio System Board. These two
96-pin rectangular DIN-type connectors carry all audio and
control signals between the Audio System Board and the I/O
Backplane Board's externally exposed connectors. The
remaining internal connector provides dc connections for the
power supply located under the Audio System Board. As
previously described, the I/O Backplane Board distributes
this dc power to the Audio System Board via DIN
interconnections. See LBI-39101 and LBI-39102 for I/O
Backplane Board connector pin-out and interconnection
details.
Audio System Board
The Audio System Board is the heart of the Enhanced
Audio Enclosure. It accommodates all audio and logical
processing circuitry for the Enhanced Audio Enclosure.
Major circuits and functions:
•
Audio Input Circuits
– These circuits provide
amplification, filtering and level-adjustment for all
audio signals applied to the Enhanced Audio
Enclosure's audio inputs. Input signals include mic
audio signals, balanced-line audio signals from the
CEC/IMC, balance-line audio signals from Call
Director equipment, and audio signals from a pager
(or similar device).
•
Audio Switching Matrix Circuits
– The audio
switching matrix routes or switches conditioned
(amplified, filtered, level-adjusted) input audio
signals to the appropriate audio output circuits.
This matrix consists of ten (10) "cross-point
switch" integrated circuits or "chips" which each
have an 8 x 8 switch matrix. All console audio
signals are routed through the matrix chips. Input
audio signals are applied to the "y" side of the