Control-S question

Is Control-S "send only"? If not, will the Control-S port on the slink-e recieve commands from the control-s as well as send commands to it?

I'm still trying to get a grip on non-CD communication. I have a VCR, with what turns out to be a Control-S cable connected to my TV. Pressing "Play" on the face of the VCR causes the TV to switch to the VCR input (which is associated by the Control-S cable being plugged into that input). What did the VCR send to the TV? At the same time (and I haven't tested this in a while so I may be wrong), I remember that if I put a box over my VCR to obscure the IR port and hit play on the VCR remote, it still starts playing, assumably from the TV relaying the command over the Control-S cable.