Sony, Panasonic, Philips.
assitant
I don’t know that either. I’m sorry.
assistant
Which company invented the first portable CD player?
user
I’m not sure. Maybe Sony?
assistant
Do you know Sony'
user
No.  Sorry, I don’t know that.
assistant
Do you know Sony's first portable CD player model number?
user
No.
assistant
Did any other companies besides Sony developed portable CD players?
user