is it possible to input audio/data from a phone to an Atari XE130 casette port?

[ELS122]

So I had taken appart the program recorder for an atari 130XE when I was a kid, and now I can't record any program...
I was looking at shematics for the program recorder and I can't really wrap my head around how it works, it seems that maybe it uses 1 the right track for music/audio effects, and the left track for the program itself but it like... amplifying it a ton... idk.

here's the shematic for the program recorder: https://oldcomputer.info/8bit/aptaperec/xc12.gif
here's a pinout for the connector (seems it's not correct, not sure...): http://www.kbrnet.de/projekte/sdrive-max/sio.png

so it seems when it records data, it just connects straight to the record head from the computer?... also how does the erase head oscillator even work?
or it just magnetizes the head? well I know nothing about tape drives so it's probably all fine there...

but the part where it gets the program data is confusing to me... do I just connect an RCA cable to pin 4 and 3?
what about the +5V/ready and Motor Control pins? I have tried inputting data into pin 3 but it did nothing. (yes I did type the load command)

and perhaps it like... converts the analog signal from the tape into digital 0/5V for the data track...  I am just completely lost on that part...

[gcewing]

Yes, it looks like the playback circuit is decoding the tones from the tape and producing a digital signal. So you won't be able to feed audio straight into the Atari's cassette port.

Here's my take on how it works: Q5 and Q6 amplify the signal from the head, then it goes through a limiter (U1C) and then to two bandpass filters (U1A and U1B) which are presumably tuned to the tone frequencies used. The outputs of those are rectified and compared by U1D, giving a 1 or 0 depending on which one is giving the strongest output.

You seem to be right that the computer directly feeds the head during recording; it must be generating the tones in software.

The right head is just connected to an audio amplifier.

I don't think there's any erase oscillator, it's just passing DC through the erase head. Which is probably fine for this application -- it hardly needs to be hi-fi!