Plantronics 1273 Manual

IPlANITIRONllCC§
Frederick Electronics
FEATURES
May be used as a half or full duplex
dev~ce,
or an independent Keyer or
Demodulator.
Highly stable and accurate tone keyer
o-utput.
Demodulator has active filter input for
improved noise rejection.
Low power consumption.
GENERAL
The Model 1273 provides a full or half
duplex connection between a digital data
device and a communications channel. The
unit is intended primarily to interface a
data terminal to an HF radio channel.
APPLICATIONS
Outstanding performance is realized in the
demodulator section, for signals derived
f.rom the HF radio band, due to independent
detection of the mark and space tones.
"AM" detection of this redundant data has
been acknowledged, by both amateur and pro-
fessional RTTY operators, to be superior to
"FM" detection techniques. Wide dynamic
range is obtained without the use of limiter
circuits. This makes possible good recep-
tion of signals with low signal-to-noise
ratios and offsets the normal deleterious
effects of frequency selective fading which
MODEL 1273
FSK
KEYER/DEMODULAlOR
APPLICATIONS
<
C ONT)
normally plagues HF radio reception. FEC
has a long and highly successful history
with design of equipment of this nature.
The tone keyer section has also been de-
signed with the requirements of an HF radio
circuit in mind. This section features
excellent frequency stability and accuracy,
spectral purity, and close output·level
control. All are highly desirable for TTY,
FSK operation on HF paths.
The Model 1273 modem may be used in any
situation where conversion of digital data
to FSK signals and the inverse are required.
This includes long distance hard wire cir-
cuits and storage or retrieval of audio
data from magnetic tapes.
The equivalent of quad-diversity performance
is realized by connecting two separate
antenna/receiver/demodulator set-ups to-
gether. This is easily accomplished by con-
necting three wires from one Model 1273 to
the other. No further equipment, such as
a diversity
combi~er,
is required.
DESIGN
The Model 1273 uses all solid-state modular
circuitry, packaged on plug-in printed cir-
cuit boards. Access to the plug-in modules
is provided by an easily removable top cover.
The unit is suitable for fixed or slide-
mounting in a standard 19" equipment rack.
FREDERICK ELECTRONICS CORPORATION
Hayward Road
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Post Office Box 502
I
Frederick, Maryland 21701
Telephone: (301) 662-5901
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Cable: FREDCO
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Telex: 893438 ~
DATE
6/74