补充体力！！！！！！
靠，这么厉害！！！
太感谢了，LZ太好了
Introduction
Long ago and not so far away, Motorola came up with a way to get more than
one Land Mobile customer on the same frequency at almost the same time. They
figured that different customers could coexist on the same frequency if they did
not have to listen to each other routinely. They invented Continuous Tone Coded
Squelch System or CTCSS for short and patented it as "PL" short for "Private
line". Other manufacturers, finding that the system was absolutely necessary to
stay competitive came up with "Channel Guard," "Quiet Channel," "Call Guard,"
and many other names for the same thing to avoid lawsuits for marketing a
patented system.
The manufacturers of amateur equipment seem to have settled on "tone" for
encode only and "tone squelch" for encode/decode. Most of the amateur VHF
and UHF equipment manufactured in the last ten years has at least encode
capability (standard or optional) and many have decode capability (standard or
optional).
When it is available, it is simply a plug in circuit board. Aftermarket encoders and
encoder/decoders can be added to virtually any transceiver since they have now
been developed smaller than a postage stamp.
The system is based on a "subaudible" tone injected after the audio stages into
the transmitter during encode and the tone is detected before the audio circuits in
the receiver. The decoder switch is then used to perform some function, usually
to unmute the receiver when the tone is decoded.
In the commercial equipment, the audio bandwidth tends to be narrower than our
amateur equipment and there are circuits installed to filter out the tones so they
are truly subaudible. Most of our amateur equipment transmits and receives a
much broader audio bandwidth and has no special tone filters, so most hear the
tones. The lower the tone frequency the less audible it tends to be.
没头绪。。。。
有用吗？？？？？？？？？？？？
{:3_41:}{:3_41:}{:3_41:}{:3_41:}{:3_41:}{:3_41:}
是真的么、、、、、、
回帖补充体力！！！！！！！！！！！
同上。。。。。。。。。。。