What’s this CTCSS and DTMF?

What is this DTMF thing all about!

DTMF (dual tone multi frequency) is the signal to the radio repeater or Node that you generate when you press an ordinary radio or telephone’s touch keys. In the Australia and perhaps elsewhere, it’s known as “Touch-tone” With DTMF, each key you press on your Radio generates two tones of specific frequencies. So that a voice can’t imitate the tones, one tone is generated from a high-frequency group of tones and the other from a low frequency group. Here are the signals you send when you press your Touch-tone radio keys pad:

DTMF Functions

In Sysop mode, Echo-Link can be configured to accept commands through the local receiver using DTMF tones (Touch-Tones).  These commands are used to enable or disable the link, or to connect or disconnect a station on the Internet.

Each command consists of a sequence of digits (or the special keys *, #, and A through D).  Although a set of default sequences is assigned to each function, any sequence can be customised using the DTMF tab of the Sysop Settings page.

The table below lists each of the DTMF commands.

Note: If you have upgraded from an earlier version of Echo-Link, you may need to choose “Reset to Defaults” to make all of the following commands available.

Command Description Default
Connect Connects to a station on the Internet, based on its node number. num
Connect by Call Connects to a station on the Internet, based on its call-sign. C+call+#
Random Node Selects an available node (of any type) at random, and tries to connect to it. 00
Random Link Selects an available link or repeater (-L or -R) at random, and tries to connect to it. 01
Random Conf Selects a conference server at random, and tries to connect to it. 02
Random User Selects an available single-user station at random, and tries to connect to it. 03
RandomFavNode Selects an available node (of any type) at random from the Favorites List, and tries to connect to it. 001
Random FavLink Selects an available link or repeater (-L or -R) at random from the Favorites List, and tries to connect to it. 011
Random FavConf Selects a conference server at random from the Favorites List, and tries to connect to it. 021
Random FavUser Selects an available single-user station at random, and tries to connect to it. 031
Disconnect Disconnects the station that is currently connected.  If more than one station is connected, disconnects only the most-recently-connected station. #
Disconnect All Disconnects all stations. ##
Reconnect Re-connects to the station that most recently disconnected. 09
Status Announces the call-sign of each station currently connected. 08
Link Down Disables Echo-Link (no connections can be established). (none)
Link Up Enables Echo-Link. (none)
Play Info Plays a brief ID message. *
Query by Call Looks up a station by its call-sign, and reads back its node number and status. 07+call+#
Query by Node Looks up a station by its node number, and reads back its call-sign and status. 06+num
Profile Select Switches to a different stored set of configuration settings (0 through 9). B#+num
Listen-Only On Inhibits transmission from RF to the Internet. 0511
Listen-Only Off Restores normal transmission from RF to the Internet. 0510

Connect

The default for the Connect command is to simply enter the 4- 5-, or 6-digit node number to which you wish to connect.  To prevent interference with other DTMF functions, however, you may wish to configure a special prefix, such as A or 99.

Link Up and Link Down

No defaults are provided for these functions.  To enable these functions, enter a DTMF sequence for each one, using the DTMF tab of the Sysop Settings page.

Profile Select

Profiles are numbered from 0 to one less than the number of profiles shown under File->Profiles.  Profile 0 is always MAIN.

Station Shortcuts

Custom DTMF commands can be created to connect to specific stations. These commands are called Station Shortcuts, and are not shown in the table above. To manage your Station Shortcuts, click the Station Shortcuts button on the DTMF tab of Sysop Settings.

Entering Node Numbers

To enter a node number (for the Connect or Query by Node commands), enter the 4-, 5-, or 6-digit node number.  If the specified node is not among the stations currently logged on, Echo-Link will say “NOT FOUND”.

Entering Call-signs

To enter a call-sign (for the Connect by Call or Query by Call commands), press two digits for each letter and number in the call-sign.  The first digit is the key on which the letter appears (using 1 for Q and Z), and the second digit is 1, 2, or 3, to indicate which letter is being entered.  To enter a digit, press the digit followed by 0.  When finished, end with the pound key (#).

For example, the letter “K” is entered as “52″, the letter “Q” is entered as “11″, and the digit “7″ is entered as “70″.

Call-signs need not be entered in full.  If a partial call-sign is entered, Echo-Link will find the first match among the stations currently logged on.  If no match is found among the stations currently logged on, Echo-Link will say “NOT FOUND”.

Examples

(These examples assume that the default DTMF codes are configured.)

  • To connect to node number 9999:

Enter:  9 9 9 9

Echo-Link responds with:

“CONNECTING TO CONFERENCE E-C-H-O-T-E-S-T”

followed by

“CONNECTED”

because 9999 is the node number of conference server “*ECHO-TEST*”.

  • To get the status of K1RFD:

Enter:  0 7 5 2 1 0 7 2 3 3 3 1 #

Echo-Link responds with:

“K-1-R-F-D 1-3-6-4-4 BUSY”

because 13644 is the node number of station K1RFD, and K1RFD is currently busy.

  • To connect to a random link or repeater:

Enter: 0 1

Echo-Link responds with:

“CONNECTING TO K-1-O-F REPEATER”

followed by

“CONNECTED”

because K1OF-R was selected at random.

Do you want to know more about Echolink go to http://www.echolink.org/

CTCSS Tones

Continuous Tone-Coded Squelch System or CTCSS is used to reduce the annoyance of listening to other users on a shared two-way radio communications channel like UHF CB and is quite often referred to as tone squelch .
Where more than one user group is on the same channel, CTCSS filters out other users if they are using a different CTCSS tone or no CTCSS. Instead of turning on the receive audio for any signal, the two-way radio receiver’s audio turns on only in the presence of a signal AND the correct tone.
A carrier squelch or noise squelch receiver is unlocked and will let any signal in. A receiver with CTCSS locks out all signals except ones encoded with the correct tone.

Following is a list of the common CTCSS Code Numbers and Frequency

Code Number Frequency (Hz)
Code Number
Frequency (Hz)
oF OFF
20
131.8
1 67.0
21
136.5
2 71.9
22
141.3
3 74.4
23
146.2
4 77.0
24
151.4
5 79.7
25
156.7
6 82.5
26
162.2
7 85.4
27
167.9
8 88.5
28
173.8
9 91.5
29
179.9
10 94.8
30
186.2
11 97.4
31
192.8
12 100.0
32
203.5
13 103.5
33
210.7
14 107.2
34
218.1
15 110.9
35
225.7
16 114.8
36
233.6
17 118.8
37
241.8
18 123.0
38
250.3
19 127.3

What is this CTCSS Thing Anyway?

by Daryl Tewksbury.

You have probably noticed that more and more radio manufacturers have been advertising that their radios incorporate the ability to use CTCSS (and other types of squelch control). So what is it?CTCSS stands for Continuous Tone Coded Squelch System. This is simply one means of controlling when the radio un-mutes its received audio. With a normal FM transceiver, the received audio is muted until a signal is detected with sufficient strength to be intelligible. The point at which this occurs is often adjustable, but with narrow band FM, a pre-defined point works perfectly well and is what is used in most of the lower cost radios. However, with the ever decreasing cost of radios has come an increase of their use, and therefore “interference”, so the manufacturers have started to incorporate CTCSS into them. A radio with CTCSS enabled simply adds a continuous tone underneath the voice during transmission. If the receiving radio has CTCSS enabled also, it will not un-mute the received audio unless it receives that same tone in the transmission. The radio is still receiving all communications on that channel, but isn’t letting you hear it unless the correct tone exists. In fact, if you use a high enough tone you may even be able to hear it in the received audio.
What tone is my radio using then? This is a good question. CTCSS has been around for a long time in commercial radios, and there are a bunch of ISO standard frequencies that are used. However, the manufacturers of these lower cost radios don’t want to confuse you with a frequency like 179.9Hz, instead they just create a tone table with a number that corresponds to one of the many standard frequencies. This could potentially make for some incompatibilities. There is nothing to say that tone 5 on one radio is the same as tone 5 on another. And there is also nothing to say that tone 5 on one radio isn’t the same as tone 3 on another.
Hopefully the radio’s manual will show you what the actual frequency for each tone number is.
Using CTCSS does not give you extra sub channels or anything as exciting, nor does it give you any privacy by scrambling your audio; anyone with another radio can listen to your transmission. It is simply a way of not having to listen to other users of that channel. However, if there are other users on the same channel that are either not using CTCSS or using a different tone, then you will not know, and potentially they could stop you from receiving anything on that channel if they are strong enough.
So if you are thinking of using CTCSS then it would be worthwhile to have a listen to the channel with CTCSS turned off for a while, to see if there is anyone else already using it. Also remember that even if people know what channel you are using they may not be able to contact you unless they know the exact tone you are using. So be cautious before deciding to use it. If an emergency situation arises, you may be flying around unaware and non-collectable.

Last update 16/05/2013

Sherbrooke Community Radio Club Inc “VK3KID”

Established 2007

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