
Installation
C-3
microprocessor control and tracks the tone frequency, so that a constant-
amplitude sine wave tone is created at any CW or paging tone frequency.
DTMF tones are generated by a
MT8880 DTMF Transceiver IC
.
Memory Protection
The controller contains circuitry to protect the data stored in RAM and to
maintain the clock and calendar even with no power applied to the controller.
A
Dallas Semiconductor DS1644 Timekeeping RAM IC
performs the following
tasks: It monitors the 5V logic supply, disables the RAM’s chip-enable input
when an out-of-tolerance condition is detected, and switches the RAM’s VCC
pin from the logic supply to the lithium battery when the logic supply falls too
low to maintain the data. The IC also contains the controller's Clock and
Calendar.
The
Lithium Battery
contained within the IC has better than a 10-year life due
to low (about 1 µA) current drawn by the RAM under backup conditions.
Cables
You will need to prepare either two or three
Cables
for the 7K controller.
•
One cable is for DC power, using the
2.5mm plug
provided.
•
One cable is for repeater connections, using the
DB25P
provided.
•
A third cable is for auxiliary connections, and is not needed for simple
installations. It uses the
DB25S
provided.
The following section of the manual describes the proper connection of the
7K’s circuits to your equipment, and the audio adjustments required.
Repeater Receiver COR
The controller requires a signal, generated by the repeater receiver, which
becomes active when an incoming carrier is detected. This signal is usually
called
COR
(Carrier Operated Relay)
or
COS
(Carrier Operated Switch)
, and is
usually generated by the receiver’s
Noise-Operated Squelch Circuit
. Some
receivers don't have a COR or COS but have a
Channel Busy LED Indicator
,
which works similarly. At this point, it is unimportant whether the COR signal is
low active
or
high active
, since the controller has sense-reversal DIP switches
(discussed later). The COR from your receiver should be connected to Pin #2
of J2 (the female DB25S connector).
To get a better idea of how to interface your particular COR signal to the
controller, let’s examine the controller’s
COR Input Circuit
. This circuit consists
of an NPN transistor, Q1A, and three resistors. Q1 is actually a DIP package
containing four 2n3904-type transistors. R10 is a DIP package containing
seven 10K resistors. R11 is a SIP package containing seven 4.7K resistors
with one common. One resistor from R10 and one resistor from R11 form a
three-to-one voltage divider. Therefore, the COR input voltage threshold is 3 x
0.7V, or about 2V. Your receiver’s COR driver must be capable of swinging
Содержание 7K
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Страница 389: ...Parts Lists and Schematics D 9 Main Board layout to be provided...
Страница 392: ...7K Appendix D D 12 SSM schematic to be provided...
Страница 395: ...Parts Lists and Schematics D 15 TIM Schematic to be provided...
Страница 396: ...7K Appendix D D 16 TIM Board Layout to be provided...
Страница 399: ...Parts Lists and Schematics D 19 ADM Schematic to be provided...
Страница 400: ...7K Appendix D D 20 ADM Board Layout to be provided...