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SECTION 1
GENERAL INFORMATION
1.1 General Description
AM
and
FM
EBS Systems
The
Models 886
and
887 EBS Systems are designed for broadcasters to
meet
Parts 73.940,
73.941, and 73.942
of
the FCC Rules and Regulations.
The
886 AM Receiver uses a frequency-synthesized local oscillator which is phase-locked
to
a 5
MHz
crystal oscillator.
It
is tunable across the AM broadcast
band
in
10
kHz
increments via a 3-digit front panel pushbutton switch.
The
886 Receiver's stability is
±500
Hz
per
year.
In
addition to broadcast station use,
the
AM
Receiver provides low cost EBS monitoring
for emergency services such as police, fire, hospitals,
and
Civil Defense agencies listening
to
EBS-participating stations during
an
emergency.
The
887
FM
Receiver is a high performance, tunable receiver.
It
uses a 3-digit front
panel pushbutton switch
that
tunes
in
100
kHz
increments. This receiver is ideally suited
to
FM
inter-city relay networks, key links
in
the EBS alerting procedure, thus allowing
pickup
and
rebroadcast
of
emergency programming without degradation
of
signal quality.
Both EBS Systems have a built-in, two-tone decoder for the 853
Hz
and
960
Hz
EBS
signaling tones from demodulated outputs. Stable piezoelectric tuning fork filters are
used
to
achieve a bandwidth
of
±5
Hz
from each tone frequency.
This integral two-tone EBS generator, which uses individual crystal oscillators, produces
the
853
Hz
and
960
Hz
tones
simultaneously, with
an
accuracy
of
±0.25 Hz.
Tone
amplitudes may
be
observed
and
adjusted individually.
Test
and on-air transmission
switches
are
provided
on
the front panel.
There
are two 2-digit
LED
displ
ays
on
the
front panel
of
both
systems.
These
displays
show the
number
of
days
(up
to
12) since EBS
test
transmissions were last received
and/or sent. Two
LED
bar
graph displays are also provided for audio
and
RF
level obser-
vations.
A speaker is provided
on
the front panel for audio monitoring. This speaker works in
conjunction with
the
rear panel volume control, which also adjusts the volume
of
an
exter-
nal speakerwhen connected to a
rear
panel phone jack.
Both receivers are configured
at
the
factory
to
operate from a 117 Vac, 50
Hz
or
60
Hz
power source.
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