RED PT500-2, Руководство по обслуживанию

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PT500-2 Service Manual
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CTCSS/DCS signal coding and decoding:
CTCSS/DCS signals from MCU (pin22 and pin18 output) are sent to VCO and TCXO for
modulation respectively after filtering by R500 R501 C500 C501 and R504 R503 C920 C921.
CTCSS/DCS signals from receiver are sent to MCU(pin52) for decoding, and then MCU test
if there are CTCSS/DCS signals with the same setting of the station to decide whether open
the speaker or not.
CTCSS (continuous tone control squelch system, hereinafter referred to as CTCSS), is a
kind of squelch control system with modulation on carrier and continuous sub-audio signals
as pilot tone. If CTCSS function is set, the call is available only at the same CTCSS
frequency of both receiving and transmitting parties to avoid the disturbance of other signals.
The station has 39 groups of standard CTCSS frequency for your selection, such as Table
5.1.
CTCSS signals produced by MCU are sent to VCO for modulation after filtered the HF
components over 300Hz in low pass filter composed by RC.
Table 5.1 CTCSS Frequency Table