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What are the CTCSS and DCS

What are the CTCSS and DCS

What are the CTCSS and DCS? In telecommunications, CTCSS and DCS are systems used to reduce the annoyance of listening to other users on a shared two-way radio communications channel.

What's the CTCSS?

CTCSS is Continuous Tone Coded Squelch System. It does this by adding a low-frequency audio tone to the voice. Where more than one group of users is on the same radio frequency, CTCSS circuitry mutes those users who are using a different CTCSS tone or no CTCSS. In other words, as long as the transmission has a different CTCSS or no CTCSS, then your radio will not pass any audio to the speaker.


What's the DCS?

CTCSS is an analog system. A later Digital-Coded Squelch (DCS) system was developed by Motorola under the trademarked name Digital Private Line (DPL). General Electric responded with the same system under the name of Digital Channel Guard (DCG). The generic name is CDCSS (Continuous Digital-Coded Squelch System). CTCSS and DCS are also referred to by other names, including CDCSS, PL,  and DPL, but the official terms are CTCSS and DCS. They both have the same function and work in similar ways.


When do you need to set the CTCSS/DCS?

CTCSS and DCS are sometimes incorrectly referred to as a sub-channel because no additional channels are created. All users with different CTCSS or DCS tones on the same channel are still transmitting on the identical radio frequency, and their transmissions interfere with each other, however, the interference is masked under most (but not all) conditions. The CTCSS feature also does not offer any security. CTCSS and DCS don’t stop anyone from listening to you, they just stop you from hearing other people. If someone has a radio with no CTCSS and DCS on, they will be able to hear everyone on the channel, including people using CTCSS and DCS.

In normal conditions, we want to hear more voice from others, so we don’t need to set the receive CTCSS or DCS. But when the repeater has requested, for example, the repeater has received CTCSS or DCS, we need to set a transmit CTCSS or DCS on the radio. Remember that CTCSS and DCS don't stop anyone from listening to you, they just stop you from hearing other people. So when you found that your radio led indicates there's a signal, but you can't here voice, please check the receive CTCSS and DCS first.

How to set the CTCSS and DCS, Most of the analog radios has two methods. We can set it on the programming software or set it via radio keypad directly. It mainly depends on if the radio support to adjust it via radio keypad.

Let take HD1 for example.

Set the CTCSS and DCS on the Ailunce HD1 software.


Open the software, Click the channel and enter the channel setting. We can see the Dec QT/DQT and Enc QT/DQT. Dec QT/DQT means receive CTCSS/DCS, only when you don’t want to receive non-CTCSS/DCS or different CTCSS/DCS signals, you can set it. Dec QT/DQT will help you filter some signals. If you want to listen to more voice, You doesn't need to set it, just keep it as none. Enc QT/DQT means transmit CTCSS/DCS.

When we check the repeater information, we can found, Some repeater has receive CTCSS/DCS request. So when we set the radio information, we need to set the corresponding transmit CTCSS/CDS. Only when we set the transmit CTCSS/DCS, the repeater can receive our signals. The receive CTCSS/DCS is no need.


Set the CTCSS and DCS on the Ailunce HD1 Radio Keypad.

After knowing how to set CTCSS/DCS on software, we can see how to set it on the radio now. Ailunce HD1 is a true VFO radio and support Front Panel Programming.

Turn on the radio. The band is FM(analog) mode, we can enter into Band A/B Set.there are three options. C-CDC, R-CDC, T-CDC. C-CDC means Transmit CTCSS/DCS and Receive CTCSS/DCS are the same. you can one key to set them. Note, when you set C-CDC, it means, you have set both Transmit and Receive CTCSS/DCS at the same time. R-CDC means receive CTCSS/DCS. T-CDC means transmit CTCSS/DCS. The most option we use is T-CDC. When we select the T-CDC, we can switch CTCSS, DCS, OFF by pressing the star key. and then by pressing up and down key or channel knob to switch CTCSS/DCS value.


Hope you this blog can help you know more about the CTCSS and DCS, and learn more about the Ailunce HD1. If you have any question, feel free leave messages to us.

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