That side selection is for LP playback on a stacked record changer.
You stack both LPs on the changer.
You play side A on the first LP, then the changer drops the other Lp to play side B next.
Then you flip both LPs over, and play sides C and D.
Record changers are no longer made for LPs.
You stack both LPs on the changer.
You play side A on the first LP, then the changer drops the other Lp to play side B next.
Then you flip both LPs over, and play sides C and D.
Record changers are no longer made for LPs.