Specifications

LBI-39100
12
matrix and output signals are sent out from the "x"
side. Audio matrix and all other logical circuitry on
this board is controlled by the on-board
microcontroller circuits.
•
Audio Output Circuits – Prior to application to
the appropriate Enhanced Audio Enclosure output,
each audio signal on the output side of the audio
matrix (a switched-in signal) is applied to an audio
output circuit. Each audio output circuit provides
amplification/attenuation, impedance matching
and/or level-adjustment in the output path. Output
paths include headset earphone audio, low-power
speaker audio ("select" and "unselect" audio),
balanced-line audio signals to the CEC/IMC,
balance-line audio signals to Call Director patch
equipment, and single-ended audio signals to call-
check recorders.
•
Microcontroller Circuits – Intel 80C32-based
microcontroller circuits on the Audio System Board
control and process all logical data signals to and
from the Audio System Board's I/O logic circuits.
These circuits include (non-inclusive listing) the
audio switching matrix, several serial ports, bi-state
logical inputs, and bi-state logical outputs. The
microcontroller circuits also read the on-board
analog-to-digital converter circuits used for VU
meter indications.
•
PC Serial Port Circuit – An RS-232 port for
control data communication with the Personal
Computer (PC).
•
Dispatch Keyboard Serial Port Circuit – This
serial port receives keystroke data from the
Dispatch Keyboard. Operating dc power is also
delivered to the Dispatch Keyboard via this serial
port.
•
Expansion Serial Port Circuit – An RS-422 serial
port which permits control data interfacing to
serially-interfaced external equipment. (Reserved
for future use.)
•
Bi-State Logic Input Circuits – These circuits
interface bi-state logical sense lines from external
equipment connected to the Enhanced Audio
Enclosure to the Audio System Board's
microcontroller circuits. Examples include mic
PTT sense lines, mic connected/not connected
sense lines, Call Director off hook, and Call
Director jack sense lines. Each circuit includes a
pull-up resistor for the external device and low-
pass filtering.
•
Bi-State Logic Output Circuits – These circuits
interface the microcontroller circuits to bi-state
logical output devices such as relay contacts. The
Audio System Board has a total of seven (7) on-
board relays.
•
Analog-to-Digital Converter Circuit – The
analog-to-digital (A/D) converter circuit's primary
function is to provide VU (Volume Unit) data on
various Enhanced Audio Enclosure audio output
signal levels. The microcontroller reads the A/D
converter and it sends the read data to the PC via
the serial control data link. VU indications are
displayed within the system status area on PC's
monitor. The A/D converter circuit is also utilized
during automated test and alignment procedures.
SPEAKERS KITS AND ASSEMBLIES
Speaker Kits used with the Enhanced Audio Enclosure
consist of mechanical hardware, one or more Speaker
Assemblies, and cables which interconnect each Speaker
Assembly to the Enhanced Audio Enclosure. For a given
Enhanced Audio Enclosure, one Speaker Assembly is the
"select speaker" and the remaining are the "unselect
speakers."
Speaker Kit mechanical hardware may be of several
different varieties providing either desktop speaker
operation in the form of a self-contained single-speaker case
or a rack-mount version in the form of a standard 19-inch
EIA rack mount assembly. Normally, rack-mount Speaker
Kits are factory equipped with two (2) Speaker Assemblies –
one select speaker and one unselect speaker. If additional
unselect speakers are required for a given console, up to two
additional Speaker Assemblies may be added for a total of
four (4) speakers in a 3-rack-unit-high assembly.
NOTE
See the table and parts lists in LBI-39104 for
Speaker Kits' contents.
Each Speaker Assembly consists of a high-quality
magnetically-shielded speaker, a Speaker Amp Board which
accommodates audio power amplification circuitry, a front
panel, a panel-mounted volume control potentiometer, and
mechanical hardware. This unit may be installed in the
desktop case or in the rack-mount frame. Since a
magnetically-shielded speaker is employed, this assembly
may be located near a video display monitor ("CRT")
without causing monitor distortion. The difference between
NOTE