Selective Calling via DTMF

[CSL126]

Hey guys, I apologize in advance if questions similar to this have already been answered...

First of all, I have two types of Tytera radios (MD 9600 and MD 380). When operating in an analog mode, is there any way to activate the radios remotely utilizing DTMF tones? I'd like to communicate with someone over a shared repeater and the selective calling ability would be nice as we're not necessarily interested in hearing everybody else's conversations.

If that feature is not available on either of those models, does anyone know of any type of external speaker that can be plugged into the radios that will activate via DTMF tones?

Lastly, is it legal to transmit DTMF over GMRS frequencies? I know that it's commonplace in amateur radio for controlling repeaters...

Thanks in advance!

 

[chief21]

Selective calling (decode) is available in most commercial radios, but most often as 2-tone or 5-tone, not usually DTMF. And I'm not sure if the encode function is often available in the mobiles and handhelds.

Some of the Chinese radios seem to be more flexible with regard to selective calling. The AnyTone 878 handhelds appear to accommodate several types of signaling, including DTMF. I've never actually used it with my 878, but the CPS application has sections for 5-tone, 2-tone, and DTMF signaling and it appears that the radio can be programmed for both encode and decode with each of these methods.

I'm not aware of any prohibition against selective calling on GMRS frequencies.

 

[WA0CBW]

Also some repeaters may block DTMF tones from being repeated.
Bill

 

[RFI-EMI-GUY]

Hey guys, I apologize in advance if questions similar to this have already been answered...

First of all, I have two types of Tytera radios (MD 9600 and MD 380). When operating in an analog mode, is there any way to activate the radios remotely utilizing DTMF tones? I'd like to communicate with someone over a shared repeater and the selective calling ability would be nice as we're not necessarily interested in hearing everybody else's conversations.

If that feature is not available on either of those models, does anyone know of any type of external speaker that can be plugged into the radios that will activate via DTMF tones?

Lastly, is it legal to transmit DTMF over GMRS frequencies? I know that it's commonplace in amateur radio for controlling repeaters...

Thanks in advance!

The use of DTMF calling was a popular aftermarket feature for land mobile radio in the 70 and 80's. There were commercial boxes you could add to a mobile radio to activate the speaker and the vehicle horn. You may find these for sale on e-bay. The Japanese LMR manufacturers built this into many radios. iCom had it as an included feature in many ham radios, though few people in the US used it, apparently in the congested band in Japan it was popular. An issue with DTMF is "twist". When connected to a radio system, the audio must be flat or the tones will decode poorly. If you connect properly to the mike input and filtered RX audio of the radio, it is not an issue.

In the US, Motorola being dominant in the market, eschewed DTMF and pushed MDC1200 as the means to alert. This feature was built into many radios, though primarily used for unit ID. GE/Ericcson/Comnet/MaCom/Harris followed suit with a similar protocal called STAR. The problem with MDC type signalling is that it is annoying to hear on every transmission if unit ID is used. Receivers have a DOS data operated squelch feature to mute it.

Bill is correct that some repeater controllers will block DTMF from passing through. Most don't but some have that feature set. If you are on a shared repeater, discuss the use of DTMF with the repeater operator so he knows why you are using it.

Another option is to consider purchasing a community repeater tone panel for the repeater so that you and others can have different "PL" tones. This would enhance the system.