6K V1.02 03-16-91
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several CTCSS modes via DTMF commands.
5.
2nd RECEIVER INTERFACING
An additional receiver can be interfaced to your controller, which can act as either a link receiver or
a control receiver. If a 2nd receiver is used, the controller requires a minimum of two additional
connections. They are: (1) Receiver COR; and (2) Receiver Audio.
If you require subaudible tone operation for the 2nd receiver, you may connect a CTCSS decoder's
output to the proper input on the controller.
NOTE: The two Receiver COR inputs, the two CTCSS Decoder inputs, and the Transmitter PTT
output each has an associated dip switch on the Main Board. These switches are used to invert, or
not invert, the appropriate signal. This means that the controller can accommodate either low-
active or high-active signals.
6.
EXTERNAL DEVICE INTERFACING
The controller has three Logic Inputs, each of which can monitor the state (ON or OFF) of an
external device at the repeater site. Since you can program the controller to detect either a low-to-
high transition or a high-to-low transition (or both), there is no need for the above-mentioned "invert"
switches on these inputs.
You can monitor such sensors as power failure, a high-temperature detector, a high-water detector,
or an intrusion alarm.
The controller also has three Logic Outputs, each of which can control (ON or OFF) an external
device at the repeater site. Power MOSFETs are used as the switching devices, which are
connected in an open-drain configuration (similar to transistors wired in an open-collector
configuration).
Each output can sink 75 mA when ON and withstand 40 V when OFF. All three outputs are
protected from transient damage.
7.
AUDIO GATING
The controller uses an 8 x 12 analog crosspoint switch IC for audio gating. This IC operates under
instructions from the microprocessor. Since all audio sources (receivers, tone generators, and the
landline) are fed into the crosspoint switch, and since all audio loads (transmitter, tone decoder, and
landline) are driven from the crosspoint switch, the controller's audio control flexibility far exceeds
simpler designs.
8.
TONE GENERATION
CW and paging tones are generated as square waves by the HD6340 Programmable Timer IC.
These square waves are shaped by a transconductance amp stage to reduce the "thumping"
characteristic heard on CW messages. (This thumping effect is caused by the DC component in
the square wave pulse train). The tone is then filtered by a 6th-order, switched-capacitor lowpass
stage to yield sine waves. The filter is under microprocessor control and tracks the tone frequency.
The result is a constant-amplitude sine wave tone that can be programmed to any desired
