#818

Episode 818
Cute little module that produces DTMF tones. Serial input interface. 8 pin package.
Encoder: www.banggood.c...
Decoder: www.banggood.c...
Be a Patron: / imsaiguy

[@RideGasGas]

The first part of my satcom career involved both carrier based and land based analog phone systems. The carrier based systems use a 2600 Hz tone to indicate hook state and then multi-frequency tones (MF) - not necessarily the same tone set as DTMF, or Touch Tone an AT&T trademark. The carrier based system was a single sideband multiplexer that channelized 4 kHz channels into 12 channel groups, and groups into super groups. The rightmost column of MF tones were used for priority buttons like Immediate, Flash, and Flash Override.

[@DARTHDANSAN]

What is DTMF ? Using your radio as phone ? I get it it’s called “ dual tone multi frequency “ but what does that mean in normal English ?

[@vincei4252]

You can download a wide variety of audio spectrum analysers for your phone. Android especially. I use eon on my phone from time to time, most recently to debug a tone coming out of my AC air hander.

[@kd4nc]

Oh I forgot to add that the captain crunch whistle used by Jon Draper was 2600 HZ en.m.wikipedia.org/wiki/John_Draper

[@bobkozlarekwa2sqq59]

Very interesting. Most TTL pads were 12 button. The 16 button version was sought by early phone hackers. The 4th column was labeled F, FO, I and P. I used these for synopsis repeater control in the late 70’s. Look up the Motorola MC14410 for generating TT. It was much more compact than your board uses. This was how we added TT to early handy talkies used with auto patch systems. Today, the cell phone did away with all of this. I remember using the first TT phone at the NY WORLDS FAIR in 1965

[@TeslaTales59]

I used to take apart early touch tone phones and make things from the very interesting keyboard. IMSAI guy- see if you can find one! Great video too!

[@jdmccorful]

Well that explains alot. Thanks for the look.

[@billpowell5931]

Great explanation and demo. Thanks.

[@PapasDino]

Oh, I long for the grand days of using the autopatch to make phone calls via the 2m repeater! ;-)

[@IMSAIGuy]

and we were all listening!

[@richardgreen9531]

Nice. Thankyou Mr IMSAI Guy for keeping me company while I have been working at home for so long. Some nice PC based audio analysis software is "Arta". It has a lot of features for audio analysis, and the documentation is really, really good (I am not associated with it, just that I have been using it in some of my work).

[@TheRetiredtech]

Pushing 2 buttons on a row or collum usually gives you a single tone.

[@nickcaruso]

Until the Captain Crunch cereal gave away a whistle which hit the 1633 iirc.

[@dennisqwertyuiop]

will look at my scope, I have 4 motorola tone and dtmf generators and have a digital readout and use my marconi modulation analyzer connect to yor service monitor, with rf,,should give you readouts

[@8-bitbitsa821]

You could likely change the 3.57Mhz xtal and get to operate at a higher frequency… upshifting it to something your spectrum analyzer can deal with ? Would be interesting to see how fast you could clock it too 😉

[@qwaqwa1960]

Might wanna figure out how to use FFT windows. I'm sure even a Rigol has'em...

[@qwaqwa1960]

Or, could be some other setting that needs tweaking so the spectrum doesn't look so awful.

[@IMSAIGuy]

I will be doing a video on that subject in the future

[@frankowalker4662]

Cool. What would happen if you sent the last four tones, (A,B,C,D), down the phone line whilst dialing ? Just curious.

[@rjordans]

Not so much anymore but you may want to look up the concept op phreaking

[@IMSAIGuy]

en.wikipedia.org/wiki/Blue_box

[@frankowalker4662]

@@IMSAIGuy @Roel Jordans Cheers guys, very interesting.

[@BrendaEM]

Why ever did Rigol try display the frequency domain--and--the FFT at the same time? If they just had the FFT, it might have been faster. Yes, I am a 1054z owner. Why also can the user turn on functions from the left buttons, but have to use the right buttons to try to turn them off? Yet they brag about their UI. Anyway, the 1000 series is otherwise useful.

[@IMSAIGuy]

stay tuned July 7 for a new scope

[@8-bitbitsa821]

Wait ! 6 parts ? Six ? 🤷🏻‍♂️

[@IMSAIGuy]

six videos, yes, you will have way too much DTMF for the next 6 days!

[@DARTHDANSAN]

What is going on ? Lol

[@Spinafication]

You might be able to use Spetran on your computer to see the tones. digilander.libero.it/i2phd/spectran.html