stations] [master and remote stations intermixed]. [Station shall have
capacity for later expansion to [_____master] [and] [_____remote] stations
[with_____handset] without sacrificing any equipment or feature
performance]. [When both wired and wireless circuitry is used, such
interface shall not reduce function or quality].
1.3.1.1
Sound Reproduction
The intercommunication system shall reproduce at all receiving stations a
30 dB dynamic range of a 40 dB minimum input signal referenced to sound
pressure level (SPL) over the frequency range of [300] [_____] to [3300]
[_____] Hz. Unless otherwise specified, SPL shall be 20 micro Pascal
(0.00002 Newtons per square meter). The root-mean square (rms) extraneous
noise (e.g. hum) level introduced by the intercommunication system shall be
at least [30] [_____] dB below the nominal signal level. Distortion,
including envelope delay, intermodulation, cross talk, and other nonlinear
source, shall not exceed 5 percent.
1.3.1.2
System Performance
Provide system with normally acceptable speech intelligibility, defined as
a score of at least 75 percent obtained utilizing the phonetically balanced
monosyllabic work intelligibility test in accordance with ANSI S3.2.
1.3.1.3
System Operation and Service Features
a.
Provide the system with a power switch and an associated pilot
light for ON and OFF operations. Include a volume switch at each
station to regulate listening volume. Unless otherwise specified,
the system shall operate on 120 Vac, single phase, 60 Hz source.
b.
All master stations shall have a "call-in" switch to provide an
audible and visual indication of incoming calls from remote
station. Individual visual indication shall identify calling
station and status, and remain actuated until a call is answered
by a master station.
c.
In addition to the manufacturer's standard identification plates,
provide engraved laminated phenolic identification plates for each
component connection and terminal identification labels, and shall
be 3-layer black on white on black, engraved to show white letters
on black background. Warning or caution labels shall be 3-layers
red on white on red, engrave to show white letters on red
background. Control switches and knobs shall be clearly marked
with their function and status. Identification strips for station
selector switches shall be located to clearly identify remote and
master stations and shall be protected by transparent plastic
inserts. Lettering shall be a minimum of 6.35 mm 1/4 inch high,
normal block style.
d.
At speaker/handset stations, lifting the handset shall
automatically cut out the loudspeaker in the station and all
conversation shall be carried through handset.
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NOTE: Regarding the text below, where noise does
not exceed 55 dB, specify hands-free operation from
distances up to 6100 mm 20 feet. In areas where the
noise occasionally exceeds 55 dB, a talk-listen
SECTION 16822N
Page 6
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