7K • Appendix C
C-2
optional Speech Synthesizer Module requires approximately 180mA more.
Power can be unregulated, since the controller contains internal regulators to
create both a 10VDC audio supply and a 5VDC digital supply. A third supply of
4.5VDC is created from the audio supply, and is used as the audio section’s
bias voltage.
Repeater Interfacing
In addition to the power supply, the controller requires a minimum of four
connections to the repeater: Receiver COR, Receiver Audio, Transmitter PTT,
and Transmitter Audio.
If you require subaudible tone operation, additional connections are provided
for a CTCSS Encoder/Decoder.
Note: Paths around the controller should not exist for either the COR-to-PTT
circuit or the RX audio-to-TX audio. Otherwise, the controller will not be able to
fully take charge of the repeater control functions.
Control Receiver Interfacing
If a control receiver is to be used, two additional connections are
required: Control Receiver COR and Control Receiver Audio.
Note: Each COR Input, CTCSS Decoder Input, and Transmitter PTT Output
has an associated DIP switch which is used to either invert—or not invert—the
signal. Thus, signals which are low-active or high-active can be
accommodated.
External Device Interfacing
The controller can sense the states of up to six external devices. Seven logic-
level power MOSFETS accomplish high-current switching (75mA).
Audio Gating
The controller uses two ICs—both of which are under microprocessor control:
An 8-by- 12 Analog Crosspoint Switch IC for main audio gating, and a Triple
SPDT Analog Gate IC for additional gating.
Extremely flexible system designs are possible since all audio sources
(receivers, tone generators, phone line, etc.) are fed into the crosspoint switch,
and all audio loads (transmitters, tone decoder, phone line) are driven from the
crosspoint switch.
Tone Generation
CW and paging tones are generated as square waves by an HD6340
Programmable Timer IC, then shaped by a Transconductance Amplifier to
reduce CW thumping. (This thumping effect is caused by the DC component in
the square wave pulse train). Tones are filtered by a Sixth-Order Switched-
Capacitor Lowpass Filter to yield sine waves. The lowpass filter is under
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