The solution to allowing DTMF pass is if our first digit is a 5 it temp turns off the muting. We have all of our Echolink commands including the node accesses start with 5.
We have little selective DTMF calling, but tell all who want to make sure their first digit is a 5. Simple and workable solution. The voltage levels on most DTMF decoders are set by the IC designer. On decoders like the 8880 and 8870 pin 3 is what the internal op-amp of the IC is producing and this parameter is determined by the IC designer. As with any IC one needs to supply the proper levels to the device to allow it to achieve what is needed. 73, ron, n9ee/r >From: Nate Duehr <[EMAIL PROTECTED]> >Date: 2008/03/28 Fri PM 02:07:43 CDT >To: [email protected] >Subject: Re: [Repeater-Builder] False DTMF Muting On CAT-1000 Controller > >Ron Wright wrote: > >> This problem has bothered IC type dtmf decoders for years. One would not >> see it as much if controllers did not mute rx-to-tx audio for security >> reasons. Some controllers allow this muting to be turned on/off. Other >> needs for passing the dtmf, such as for echolink, can be useful. > >Or just because muting DTMF gives a FALSE sense of security... turn >muting off and let the users use all those fancy features in their >modern rigs for DTMF paging, etc... is what we decided to do. > >It also makes it a lot easier for us to hear when someone's "frustrated" >that the "darn thing" won't respond (IRLP, the controller, whatever >feature they're trying to use) and we can hear that their DTMF is >ultra-hot, distorted, and generally crappy. > >We have one user who's using some very old odd-ball Icom rig that has a >pre-amplifier adjustment on the mic, and Icom kindly stuffed the DTMF >through it... so the DTMF from his rig goes up and down with his mic >gain settings. It took three on-air rounds of me explaining what I >could hear was happening to him -- and now instead of fixing it, he just >turns the gain down for DTMF and back up to talk... and often forgets to >turn it back up... > >"X1XXX for the IRLP... [fiddling noises with the pre-amp then digits >that still sound horrible but the IRLP can barely decode them]... [IRLP >announces it's connected]... This is X1XXX calling CQ via IRLP. [So low >deviation you can only tell it's him if you turn your rig all the way up.]" > >If we were muting DTMF, we'd have had no idea why he was complaining. > >And he STILL complains that it must be "something wrong" with IRLP. > >> It is rather difficult to state a proper level for there are so many >> variables in the dtmf audio; level, twist and level of each tone, and >> varying levels with the 8 tones. I usually set to about 3 V p-p from a >> center digit. > >This voltage is controller design dependent... stating a "general" rule >for any particular design is probably not as good as asking the >manufacturer what they design to for their op-amps, etc. > >S-Com specifically calls out 2V P-t-P at various stages in their >designs, for example. We almost never see DTMF falsing on our 5K and 7K >controllers. > >Nate WY0X > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
