This is my latest video update on the rotary phone project, in it's basically 99% finished form. It's an antique rotary phone that makes calls through the 2G network. Enjoy!
Great question! It's using a hybrid circuit to interface the ingoing and outgoing audio signals between the rotary phone and the GSM module. Basically the extra earpiece and mouthpiece (as well as the black box at the front right corner of the table) contain all the circuits of a 2nd rotary phone wired up as an analog "mirror image" used for impedance matching to minimize echoes in the audio. Without it the person on the other end hears their own voice echoed back when they speak. From an analog perspective it has all the old school central office circuitry: en.wikipedia.org/wiki/Telephone_hybrid I've actually made some updates to this since I made this video. Those mouth and earpieces are now mounted under the table in an insulated glass jar out of view and the Arduino and GSM module are no longer inside the metal box, which wasn't very effective for shielding anyways.
I live in Seattle and 2G coverage is kinda spotty but generally not too bad. My apartment gets good 2G signal. Strange thing is that in some areas if I stay in one place the coverage comes and goes. There are also some dead zones in the city where I get nothing.
@@danebeck7900 It's definitely not what it used to be. Weirdly enough the 2g coverage fluctuates throughout the day. At 12pm it's horrible but at 1am it's great. If I go into town I get full bars and great voice quality but by my house it varies a lot.
Holy crap this is good. Congratulations.
Thanks! Looking forward to the video of your own rotary cell phone!
Really nice!!!
Thanks! It needs to be redesigned though because I don't get 2G service on it anymore.
Amazing. Puts my little phone to shame. :-) What are the earpiece/mouthpiece elements under the glass doing?
Great question! It's using a hybrid circuit to interface the ingoing and outgoing audio signals between the rotary phone and the GSM module. Basically the extra earpiece and mouthpiece (as well as the black box at the front right corner of the table) contain all the circuits of a 2nd rotary phone wired up as an analog "mirror image" used for impedance matching to minimize echoes in the audio. Without it the person on the other end hears their own voice echoed back when they speak. From an analog perspective it has all the old school central office circuitry: en.wikipedia.org/wiki/Telephone_hybrid
I've actually made some updates to this since I made this video. Those mouth and earpieces are now mounted under the table in an insulated glass jar out of view and the Arduino and GSM module are no longer inside the metal box, which wasn't very effective for shielding anyways.
Wow. You're so lucky that you get good 2g coverage in your area. Where I live it's very spotty.
I live in Seattle and 2G coverage is kinda spotty but generally not too bad. My apartment gets good 2G signal. Strange thing is that in some areas if I stay in one place the coverage comes and goes. There are also some dead zones in the city where I get nothing.
@@danebeck7900 It's definitely not what it used to be. Weirdly enough the 2g coverage fluctuates throughout the day. At 12pm it's horrible but at 1am it's great. If I go into town I get full bars and great voice quality but by my house it varies a lot.
wow