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。
Meat and Potatoes of CTCSS（CTCSS的基本内容）
The system is designed around a set of relatively low frequency tones (32 or 38 depending on which 'standard' you use) ranging from 67.0 Hz to 250.3 Hz. The tones are a perfect sine wave and the frequency tolerance is very tight, typically /- 0.5 Hz. The tone is encoded and injected into the transmitter after the audio shaping circuits. The frequency deviation (level) is typically 0.4 to 0.8 kHz which is rather insignificant when compared to the typical 5 kHz voice deviation.
CTCSS系统的设计是围绕一组低频率音频信号进行的（35 或38，根据不同的标准），范围从 67.0-250.3Hz。这些亚音信号是完全正弦波，且频率差很要求很严格，通常为 /-0.5Hz，这个音频信号在声音调制电路后被注入发射器。这个频率的级别通常在 0.4-0.8KHz，当然，比起5KHZ 的语音频率范围来说，仍然是可以被忽略的。
In the receiver, the tone is detected right off the discriminator before any audio processing and decoded allowing the receiver to unmute. Commercial radios filter out the tone, but our amateur radios do not so the tone is usually noticeable. It is sometimes mistaken for a power supply hum.
在接收器一端，亚音频检测器在任何音频处理前检测音频信号，如果可以翻译出亚音频信号，则允许接受机接触静音状态。通常商业电台会滤掉这些亚音频，但我们的业余电台并不进行过滤，所以我们可能能听到这个频率的音频。有时候，亚音频会被错误的认为是电源交流声。
CTCSS does not alleviate RF interference. If two FM signals are on the same frequency at the same time, there will still be a heterodyne or beat note (unless one is 6 dB stronger than the other). But if CTCSS is being utilized and both systems use different CTCSS tones, they will not have to listen to the other system's traffic.
CTCSS 并不会降低无线电射频信号的干涉。如果2个调频信号同时出现在同一频点上，仍然会导致“撞车”，除非有一个信号的强度高于另一个6dB，以上。但如果CTCSS在2套系统中同时被应用，并设置了不同的亚音频，则他们就不会互相听到对方系统的通讯了。
With the advent of commercial repeater stations, several customers can use the same repeater without listening to each others' transmissions. In a commercial installation, the microphone hanger is grounded and when the mic is hung up, the decoder is turned on, thus muting the receiver. When the operator picks up the mic, the decoder is disabled and the receiver becomes 'carrier squelch,' hearing everything within range. If nothing is heard, the call is made. If another user is heard, they are supposed to monitor until the traffic clears and then make their call. Base station mics have a 'monitor' button next to the PTT button to disable the decoder, allowing the operator to check for traffic.
当商业转发台（中继台）诞生后，多个用户组可以通过一个中继台通连而不会互相听到话音。在商业台站，电台座接地，当麦克风被挂起时，解译静音启动，于是接收器处于静音状态。当操作员拿起麦克风，解译静音会关闭，并且接收器会被置于“载波静音”状态，并接收频率范围内的一切信号。如果没有任何信号，则允许发射。 当有其他用户时，他们可以监听，并等待传送结束并进行他们的发射。基地台的麦克风PPT键旁有一个“监听”按钮，可以手动关闭解译器，以便操作员监听。
Amateur radios do not have this automatic feature since the CTCSS system is used to allow users to restrict what they want to listen to, not to allow several fleets of radios to operate on the same frequency. Most handheld radios that can be factory equipped for full CTCSS encode and decode have a monitor button, usually around the PTT bar. Unfortunately, amateur mobiles have to manually turn off the tone to monitor the channel in the carrier squelch mode.
业余电台并不设置这项自动功能，因为CTCSS系统是允许用户自行限制他们想要接收的信号，而不是在于区别不同的用户组在同一个频率上工作。大多数手持电台在制造中装备了全部CTCSS编译及解译功能，并在PPT按键附近具备了“监听”按键。但很可惜，业余电台必须进行手动操作关闭亚音，才能转换到载波静音（噪）模式进行工作。
Some repeaters use CTCSS decode to keep from being keyed up by distant stations using other co-channel repeaters. Others use CTCSS to keep all but subscribing members off the repeater. If the intent of the repeater operator is to restrict the access to members only, it is called a closed repeater.
一些中继台使用CTCSS解译静音模式以避免一定距离以外的使用同频率的中继台的干扰。也有一些用来禁止为核准的人员使用中继。如果中继台操作员的意图在于限制使用权限的话，这个中继台则被称为限制级中继台。
