I already wrote to you - you need to distinguish between input / output:
- By connecting headphones to the phone, the sound goes from the phone to the headphones meaning you have "output / OUT"
- By connecting headphones to the headphone jack in the tower the sound goes from the tower to the headphones so you also have "output / OUT"
- You tried, or rather connected the output to the output and hence the result
- At the back of the tower you have "IN" sockets, i.e. input, so the correct solution is to connect a telephone with the "output" socket to the "input" socket (the music comes out of the phone and enters the tower)
I can't do it simply