New to cycles, what is this wire?

[arealhuman]

Fixing up this bike and using it to learn the basics of how it works, was wondering what this black cable is that runs vertically and seems to have two wires.

 

[bosco659]

Rear brake light switch.

 

[DaveO]

Wow, that's a very clean bike. No-one yet has asked for pictures. We like pictures. It's our "thing".

Welcome to the forum, by the way.

Dave

 

[Adamc]

What they said.
Plenty of pics during progress please.

 

[Raymond]

Hi Real Human and welcome to this little madhouse.

Bosco has correctly said that is the brake light switch, but I sense there might be a question behind the question? Is there something ain't working? Tell us more about how you are fixing the bike, what jobs you are doing - plenty of people on here to offer advice and help. And as @DaveO & @Adamc already said, pictures keep us happy.

 

[gggGary]

Welcome aboard @arealhuman
We'd love to hear more, as @DaveO sez that's an extraordinarily clean (74-75?) XS650!
You've either done a cubic ST of work already or were blessed to find such a speciman!