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SECTION 1: DESCRIPTION
&
SPECIFICATIONS
1.1 DESCRIPTION
The Model BP300 is a portable, two-channel inter-
com user station. The user station is designed to be
used in a full duplex, conference line intercom sys-
tem.
Conference Line Intercom Svstem (Figure 1-1)
A conference line intercom system allows a group
of people t o talk and listen on a single channel.
On this channel, all users can listen when one or
more other users are talking (conferencing). Up
to 75 users
can
share the same conference line (or
conference bus).
Full duplex operation allows two way conversation
at the same time, that is, one user can interrupt a
second user while the second user is still talking.
The BP300, with a headset, interfaces a human user
3
t o the intercom system. The user talks and listens
using the headset (or a handset). The headset con-
nects to the BP300 via a four conductor cable and
connector (optionally five or six pin). The BP300
connects to the system using a three conductor
"microphone" type cable. The BP300 contains four
controls: the volume control, the latching micro-
phone switch, the momentary microphone switch,
and the channel select switch.
On the Model
BP300L, the momentary microphone switch is re-
placed with the call light button.
Volume Control
The volume control on the BP300 has a wide range
to compensate for: user hearing differences, ambi-
ent noise variation, variations in headset
/
handset
sensitivity, and variations in voices. The volume
control in the BP300 reduces distortion by driving
the headphone amplifier only as much as needed.
Microphone Switch(es1
In normal system operation, one or more users talk
and the others listen. A microphone switch on each
station allows the talker's microphone to be enabled
and allows the listeners to keep their microphones
disabled. In this condition, speech intelligibility is en-
hanced since background noise from other micro-
( )
phones is not present.
L l '
On the Model BP300, a latching switch or momentary
push button turns the microphone on.
The momentaty push button allows quick 'bursts of
communication, especially useful in a high noise envi-
ronment. The latched position allows "hands freen
operation, when the user needs to have two way
conversation while performing another activity.
The Channel Select Switch
A channel selector switch allows a choice of two
(optionally three) channels. When the switch is on
the "1" position the station talks and listens on chan-
nel 1, on the "2"position, channel 2, and so on. On
larger systems the "1" position may be any system
channel (1 through 12 for example). Similarly, for
position
"2".
See Section 2.1 for DC powering re-
quirements under these conditions.
Call Light Push Button (BP300L, only)
Pushing this button transmits a call signal to all other
units on the channel selected by the channel selector
switch. A call signal on this channel will cause the call
light push button to flash. The flash rate is 2 to 5
times a second. The call signal itself is a 20 kilohertz
signal.
Options (-DL,
-E, -3CH,
-USMB, -LP)
The BP300 and BP3OOL use the CC33 card
except
as
indicated below. Codes at the end of each aragraph
indicate the card used. Codes are: *CC33 car$ **CC4O
card, ***CC45 card.
(CC33 schematic is SD1464;
CC40/CC45 schematic is SD1427).
-DL: Dual Listen on two channels. The volume control is
changed to
a dual
concentric potentiometer with two knobs.
The channel select switch routes the
talk
signal. The outside
knob follows the channel selector. The inside knob is the
non-talk, listen only channel.
-E:
Program Input, balanced. Deletes line loop-through,
the balanced program is fed in instead. Pins 2
and
3 are the
input connections.
A dual
concentric potentiometer with
two knobs provides separate level controls for interwm
and
program.
-3CII: Three CHannel operation. Line and loop-through
connectors are changed to 4-pin from 3-pin. A 3-position
channel select switch replaces the 2-position switch.
-USMB:
UnSwitched Microphone output, Balanced.
Deletes line loop-through. Level: -7dBm to S3dBm. The
USMB
provides
a
line level microphone signal to other
systems such
as
an Interrupted Feedback System
(IFB),
telephone, radiotelephone, or Stage Announce.
-LP:
Local
Power source. A small module converts AC line
power to low volta e to
wer the user station,
a
separate
connector
is provib;d.
# e unit does not use power from
the interwm line.
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