Low Voltage CTCSS Encoder/Decoder
5
MX165C
Pin No.
18
PTL
Signal
Type
input
Description
In RX mode this pin operates as a ‘Push To Listen’ function by
enabling the RX audio path, thus overriding the tone squelch function
(Parallel Mode). In Serial Mode this function is loaded serially.
Internal pull-up to V
DD
19
RX AUDIO OUT
output High pass filtered RX AUDIO OUT. This pin outputs audio when
RX TONE DECODE = logic 0, PTL = logic 1, or when Notone is
programmed (see Table 4). In TX mode this pin is biased to V
DD
/2.
output High pass filtered TX AUDIO OUT pin. In TX mode this pin outputs
audio present at the TX AUDIO IN pin. In RX mode this pin is biased
to V
DD
/2
output Output of an internally generated V
DD
/2 bias level that would
normally be externally bypassed to V
SS
via capacitor C6.
input
In TX mode TX AUDIO IN may be prefiltered, using the TX Audio
path, thus helping to avoid talk-off due to intermodulation of speech
frequencies with the transmitted CTCSS tone. Internally biased to
V
DD
/2.
Input to the audio high pass filter in RX mode. Internally biased to
V
DD
/2.
Input to the CTCSS tone detector. Internally biased to V
DD
/2.
Table 1: Signal List
20
TX AUDIO OUT
21
22
V
BIAS
TX AUDIO IN
23
24
RX AUDIO IN
TONE INPUT
input
input
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