I have an old Radio Shack 43-228A Telephone Recording Control from the 80's that I am trying to find the schematic for. What I'd like to do it replicate the circuit (which has a record AND play slide switch) so I can play audio from an Adafruit 1788 audio player (Along with my Arduino UNO R4) into the phone line while talking. Has anyone tried this? Any notes, schematics, etc.?

Thanks in advance!

Mike

 

I have an old Radio Shack 43-228A Telephone Recording Control from the 80's that I am trying to find the schematic for. What I'd like to do it replicate the circuit (which has a record AND play slide switch) so I can play audio from an Adafruit 1788 audio player (Along with my Arduino UNO R4) into the phone line while talking. Has anyone tried this? Any notes, schematics, etc.?

Thanks in advance!

Mike

You can couple < 3kHz audio onto a POTS line with a 1:1 audio isolation transformer.

 

You can couple < 3kHz audio onto a POTS line with a 1:1 audio isolation transformer.

Excellent thanks for that! I am 59 now and my days of remembering anything are pretty much gone! I'll look up a simple schematic for that, unless you happen to know of one... thanks again!

 

I do not recognize the RS number, is that the module for recording from the phone line?? I am not sure if it works in both directions, but it will be very simple to try.

 

I do not recognize the RS number, is that the module for recording from the phone line?? I am not sure if it works in both directions, but it will be very simple to try.

Thanks for the reply. There is actually a slide switch for "play" and "record". I have been trying to find a schematic of it as my reverse engineering days are long over (if they ever existed at all) but I did find a YouTube video. Just search for "MT8870 DTMF Decoder with Phone Line Interface"

 

YES!, that is the same Radio Shack device then. I have had several of them, never used them because they were not what I needed. They came in "box lots" from clearance sales, $5 for a large box, often ten pounds, of items of all kinds.
You will need to experiment, the larger plug is the audio signal, the small plug is to switch the motor on, for a typical cassette recorder/player from that era.

 

This might be helpful to you:

https://www.prosoundweb.com/properly-interfacing-audio-and-pots-plain-old-telephone-service/