So how close does this device come to what you need?

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I suggest you look at page 108 of the linked book.

Thank you sir. I may have the wrong book...

 

So how close does this device come to what you need?

Thanks. Nope. That item is an encoder and probably not DTMF. For vandals protection, there is nothing outside the door at the protected site to avoid destruction, not a keypad nor even a door knob. The door can be opened only from a solenoid activated by the radio receiver inside. Has to be decoding a DTMF sequence of 4 digits. The TX encoder solved by using a talkie with keypad (or a mic with it) instead of/at adding a toner (first image) at a base station transmitter.

 

Thank you sir. I may have the wrong book...
View attachment 354378

Yeah, my link sucked. This should work.

https://ia800500.us.archive.org/8/items/EngineersNotebookIIAHandbook/Engineer's Notebook II A Handbook Of Integrated Circuit Applications - Forrest Mims_text.pdf

Yep, that link works.
Ron

 

Same here. However, while inexpensive these Chinese modules aren't exactly bursting with data sheets. This is an example of what I played around with.
View attachment 354351
Fortunately the I/O pins are clearly marked up. The jack is just another signal in.


Then I suggest you Google "Cipher Locks Circuits". While I see no need for DTMF you can use it if you like.

While you oppose using a uC using a single simple uC with a module like I posted above would make this project much easier. However that is your call.

Ron

https://www.mouser.com/datasheet/2/268/mt8870d_datasheet_oct2006-1954007.pdf

 

Making one is not hard, I suspect that you're going to have to make what you want they may not make them anymore and they may not be selling them anymore.

 

eBay maybe.