CTCSS, PL, Tone Squelch
Introduction 介绍
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.
不久以前，MOTOROLA公司开始使用一种方法使多于一个的手机用户可以在同一个频率内使用。他们得出这样的结论，不同的用户可以在同一个频率上共存，只要他们不需要程序性的相互收听。于是他们创造了连续音频编码静噪系统CTCSS，并注册了 PRIVATE LINE，作为专利。其他制造商发现了此系统对于保持竞争力的必要性，于是也相继注册了'Channel Guard,' 'Quiet Channel,' 'Call Guard,'等其他名称，以逃避专利问题。
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).
业余设备制造商选择了“TONE ”作为 编码支持的代名词，而 “TONE SQUELCH”作为 编码/解码的代名词。 大多数近10年内生产的业余VHF UHF设备至少包含了“TONE”支持，（标准配置或选装），也有不少同时支持解码（标准配置或选装）
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.
“亚音片”通常是一快可插拔电路板，由于现在它的大小可以被制作得比一张邮票，所以几乎可以方便的填加如任何无线电收发设备。
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.
这套技术的基本原理如下，进行编码（调制）的时候，一个“亚音”音频信号被注入声音信号，并在接收端的音频电路前检测这个音频信号解码。于是解码（解调）转换开关可以根据这个音频部分做相应的动作，通常是，当这个 TONE被解码后，接收电路会开启声音。
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.
在商业设备中，声音频宽比业余设备更窄些，并且，配备有专门的电路用于过滤音频，于是，这些音频信号真正的成为了“亚音”，不会被听到。而大多数业余设备则在发射和接收的时候处理更宽一些的声音频宽，所以，通过大部分这样的设备能够听到音频信号。当然，这些音频信号的频率越低，越难被听到。
