In telecommunicationsContinuous Tone-Coded Squelch System or CTCSS is one type of circuit that is used to reduce the annoyance of listening to other users on a shared two-way radio communications channel. See squelch. It is sometimes referred to as tone squelch. It does this by adding a low frequency audio tone to the voice. It is sometimes referred to as a sub-channelbut this is a misnomer because no additional channels are created.
All users with different CTCSS tones on the same channel are still transmitting on the identical radio frequencyand their transmissions interfere with each other; however; the interference is masked under most but not all conditions. A receiver with just a carrier or noise squelch unmutes for any sufficiently strong signal; in CTCSS mode it unmutes only when the signal also carries the correct sub-audible audio tone.
The tones are not actually below the range of human hearing, but are poorly reproduced by most communications-grade speakers and in any event are usually filtered out before being sent to the speaker or headphone. CTCSS can be regarded as a form of in-band signaling. As a simple example, suppose a two-way radio frequency is shared by a pizza delivery service and a landscape maintenance service.
The landscapers have to listen to the pizza shop and the pizza shop has to hear about landscape activity. This is supposed to reduce missed messages and the distraction of unnecessary radio chatter for the other users.
Note that in the example above there are only two co-channel users. In dense two-way radio environments, many separate groups may co-exist on a single radio channel. The disadvantage of using CTCSS in shared frequencies is that users cannot hear transmissions from other groups.
They may erroneously assume that the frequency is idle and then transmit at the same time as another user, thus interfering with the other group's transmissions.
For example, in the above situation, a landscaper might be communicating with another landscaper. Meanwhile, a pizza delivery driver—not hearing any transmissions—assumes that the frequency is clear and calls their dispatch office. The two simultaneous transmissions could interfere with each other—resulting in one or both not being understood.
Continuous Tone-Coded Squelch System
The more groups that share a single frequency and the more frequently they transmit, the more likely that this accidental interference will occur. Radios equipped with the "Busy Channel Lockout" feature will prevent transmitting in this case.
Radio transmitters using CTCSS always transmit their own tone code whenever the transmit button is pressed. The tone is transmitted at a low level simultaneously with the voice. The tones are usually referred to as sub-audible tones.
The ability of a receiver to mute the audio until it detects a carrier with the correct CTCSS tone is called decoding. This is called the monitor function.Orange, Calif. Com-Spec is also the source of the Selectone line of products. Note: Com-Spec will sell direct to the end user and can easily beat Hutton's, Tessco's and most others prices.
Call or from am to pm Pacific time zoneMonday to Friday. If you have any data sheets that are not included below, please let us know! We can have them scanned and then return them to you. In the land mobile e. The most famous is Communications Specialists, listed above, and whose products are on this page. Then there is Connect Systems Incorporated, which made repeater tone panels for the commercial market and autopatch equipment for the amateur market.
They are located in Ventura, in Southern California their previous address, still on the title pages of some of the downloadable manuals, was in Torrance, California and they have their own web page at this web site. Copies of the manuals are on the "Other Manufacturers" page at this web site. If anyone has copies of other manuals we'd appreciate a chance to scan them. The three CSI companies are not and were not linked in any way except in the minds of a few clueless customers.
Many of the Com-Spec encoder products had a low output impedance which can load down other circuitry when connected. This is not a design fault of the Com-Spec product. Depending on the application it may be necesary to add a series restor between the encoder and the destination circuitry.
The value of the resistor will range from 1k to 47k depending on the application. It was a stand-alone high pass audio filter board similar to the one contained in the TS or TS and is easily duplicatable on perfboard. The PC board had a range jumper - if the unit does not produce the correct tone you need to check for the absence or presence of the jumper. There was also a ME version of this that was in a plastic box with a rotary switch on the front and 12 tone element sockets inside.
What are the CTCSS and DCS
To change the duration of the reverse burst adjust the value of C3 or R Also, this circuit will work in any system that uses a reed-based decoder and also with some electronic decoders. It may not function with some newer radios because some manufacturers i. Motorola use degrees phase shift for reverse burst instead of the degrees that this unit provides.
Encode only. Uses 12 DIP switches to select tone frequencies and a rotary switch to select a particular preset tone. Later on a kit was developed that added it.
Just program it for zero hang time, then connect it to the repeater controller as if it was an external CTCSS decoder which it is. While this is a terrific unit do not plan on using the internal IDer in amateur radio repeaters. Then is the main manual, including schematics, system parameters, level adjustments, over-the-air DTMF programming information, PC board layouts, and more.
IC version. Note that the hangup pin must be grounded or it won't decode. This is the single most common installation error.This is like a mains hum on the modulation, a constant musical note The receiver can be set to only open its squelch if this tone is received. Any interference would not have the correct tone present, and so the radio would remain quiet.
CTCSS was developed into a system with numerous standard tones to choose from, often When CTCSS is used, the audio is filtered out below about Hz, so that the only audio frequency energy that ends up being transmitted between 0 and Hz is the CTCSS tone itself almost always any one tone between 67 and The tone is then sometimes called 'sub audible' because it's below the range of THEN audible voice frequencies - but it would be audible if played on full range speakers without the filtering that CTCSS radio receivers also use on receive we can hear down to 20Hz or so.
The most common tone for or FRC District 5 is This helps us from hearing other systems on the same frequency from other Florida Distracts when conditions are rolling.
These stations are not "Bleeding Over" that is something completely different. They have the same rights on the frequency that you have. This data is sub-audible with most of it's energy below Hz. However is does have a wide bandwidth from 2 to Hz.
Each code word is unique and all code words may be used on the same channel without interference. A poor low frequency response in the transmitter or receiver may not seriously distort a single frequency tone signal but may seriously degrade a wide band signal containing multiple frequency components. The distortion risk is especially high if the frequency response delays the wide band frequency components.
DCS is operated at a low baud rate This requirement means that certain transmitters and receivers must be modified before they are capable of DCS operation. Phase modulators, in particular, need special consideration because they theoretically are incapable of being directly modulated by dc, unlike direct FM modulation methods.
CTCSS Encoders Decoders / DCS Encoders Decoders
Low frequency response is the primary requirement for DCS systems. You will find that it is extremely important for the receiver and transmitter to be on frequency to achieve maximum performance of the DCS function.
Errors in the transmitter and receiver frequencies show up a the discriminator output as a step function. Because of the long time constant required for the low frequency response, a step function can block the decoder momentarily.
With DCS, error correction is necessary. But if too many errors occur, you may experience some blocking out of the decoder. Errors can occur because of unwanted low frequency energy. The DCS decoders can be effected by voice energy that falls below Hz. Some radios do not remove this energy before transmission and can cause voice blocking of the decoder.
A sub audio filter that removes this low frequency energy before the audio is re-transmitted is necessary for reliable DCS operation.
Tiny Tracker.Visit us on Facebook! SafAlert Notifier. DCS Digital-Coded Squelch decoding requires receiver with discriminator or demodulator unfiltered output. Improved 2-tone decoding captures "stacked" pages. External serial port control to operate relay or PTT circuit. Read on for complete description OR see the online User Manual.
For ordering information, click here. This is the sampling rate. With time and magnitude data, the software first processes each batch of samples by applying a band-pass filter or window, thereby ignoring any frequencies outside the range ofHz. Another filter searches for continuous tones, ingoring noise, voice and digital communications.
The tone frequencies are displayed immediately on screen. Now, simply enter the two frequencies into a two-tone alert radio to be alerted any time that tone-out is sent. Receive dispatches on your mobile phone or email with SafAlert Notifier.
Safesecure shopping with PayPal. You do not need a PayPal account. Protect your computer with ComTekk's exclusive ohm isolator with DC blocking, "hot chassis" and surge protection. Recommended when connecting to base station equipment or twisted-pair lines.CTCSS DECODER - SDR
The cap code can be calculated using either the filter codes or filter frequencies. PageTone can also find the page tones that correspond to a given capcode. Be sure to check the system requirements before placing your order. By purchasing or installing this software, you agree to the terms and conditions set forth in the License EULA.
Your temporary activation key will be delivered via the email address you provided immediately after purchase. Please check your spam filter and allow up to 4 hours before contacting Support. Low-cost scanning receivers Starting around a hundred dollars, these basic units are great for monitoring analog communications and are compatible with our 2-Tone Decoder These scanning receivers may be programmed to trigger on 2-tone alerts, once you have obtained the tone frequencies using ComTekk's MultiDecoder.
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Free Download. Enter your search terms Search:.Basically what it does is this: it adds a tone into your transmission at a certain frequency. When CTCSS is used, the audio is filtered out below about Hz, so that the only audio frequency energy that ends up being transmitted between 0 and Hz is the CTCSS tone itself almost always any one tone between 67 and DCS works the same, apart from it being digital instead.
It stands for Digitally Coded Squelch. It sends a number repeatedly encoded in digital as you speak, in the low frequencies so you do not hear it. If someone else transmits on the channel with a different or no DCS, the radio will not unmute. If they transmit with the same DCS as you, then your radio will unmute. Each code word is unique and all code words may be used on the same channel without interference. A poor low frequency response in the transmitter or receiver may not seriously distort a single frequency tone signal but may seriously degrade a wide band signal containing multiple frequency components.
The distortion risk is especially high if the frequency response delays the wide band frequency components. You will find that it is extremely important for the receiver and transmitter to be on frequency to achieve maximum performance of the DCS function.
Errors in the transmitter and receiver frequencies show up a the discriminator output as a step function. Because of the long time constant required for the low frequency response, a step function can block the decoder momentarily. With DCS, error correction is necessary. But if too many errors occur, you may experience some blocking out of the decoder.
Errors can occur because of unwanted low frequency energy. The DCS decoders can be effected by voice energy that falls below Hz. Some radios do not remove this energy before transmission and can cause voice blocking of the decoder. A sub audio filter that removes this low frequency energy before the audio is re-transmitted is necessary for reliable DCS operation.
I tried the instructions to make the rt talk to the h it did not work, are there more detailed instructions for the rt and the h If question, please email us: partner retevis. If you have a check on softwareyou will find they are together in one line. Both OK. No difference when using.Small size makes it ideal for handhelds and mobiles. A mini plug and socket, with color coded wires attached, allows easy hookup, double-sided tape is supplied for mounting.
ARDUINO CTCSS decoder
Field programmable to 64 tones from Crystal controlled for high accuracy and stability. Reverse burst ms encode for squelch tail elimination. Time-out timer, programmable to 8 settings. Busy channel lockout with busy tone when time-out time is exceeded. Decode sensitivity: 15mv, impedance 60K ohms AC coupled. Decodes off discriminator output, impedance 1 meg, response time ms nominal. Small size makes it perfect for handhelds and mobiles.
Installs with mounting tape and on-board mini plug and wire set. Same circuit as the TSbut with an on-board DIP switch to allow tone selection without soldering jumpers.
All 64 tones are accessible via the 6 position mini DIP switch. The TSDS measures 1. Same circuit as the TS Chassis pins extend from the bottom of the board.
This facilitates direct plug-on to special application boards that are designed to be plugged into many popular radios. Also features an on-board DIP switch to allow tone selection without soldering jumpers. Size: 1. Compatible with all digital tone coded squelch systems used in Land Mobile radios. Field programmable by wire jumpers to all octal codes, as well as transmit and receive data polarity.
Immune to RF. Crystal controlled CMOS microprocessor for low voltage operation. High pass filter included. Solid state receiver muting with automatic monitoring, provides high or low outputs. Auto squelch tail elimination. Open collector transistor for PTT keying.
Test code to set transmit modulation level. Features Field programmable to 64 tones from Specifications Size:. Features Immune to RF. Specifications Size: 1.Want to go back to the main page?
Click here to return directly. Menu: Main Version: April 27, Revised: v1. Here is a very low cost versatile, accurate and super-stable CTCSS tone encoder module which should be ideal for your requirements. A continuous low level audio tone in the range of 67 — Hz is mixed with audible — Hz speech when transmitting. Each group of users sharing the repeater is assigned a specific CTCSS tone by the repeater operator or owner. This tone decode signal is used to enable the receiver audio in user radios.
In this way, each user only hears calls for their group. The calls between other users on the shared repeater remained inaudible. This also prevents one user group transmitting over top of another. This approach significantly increases channel occupancy and leads to improved spectrum efficiency. Table 1: The output of the CTCSS tone encoder module can be varied over a wide range but the maximum output level depends on the supply voltage.
Table 2: Version A Tone Selection. Table 3: Version B Tone Selection. This is the approach I used for m elderly Tait T transceiver. The DC isolating capacitor noted earlier was substituted for R2 on the module for this transceiver.