Sustain Pedal Question

[mrmrcoleman]

Hello, I have been looking through this schematic...

http://www.generalguitargadgets.com/diagrams/cssussc.gif

Could somebody explain to me what the LED/LDR shrink wrapped together are used for?

Thanks in advance.

Mark

[toneless]

The "shrink tube" is there to keep external lights away from the led.

[mrmrcoleman]

Sorry, my question was badly worded.

What I meant to say is, 'What does pointing an LED at an LDR achieve?

Mark

[Nasse]

Maybe googling "negative feedback" gives some answers

But I quess it reduces gain and gives that compression effect

Edit Edited a typo and I hate my day job

[StephenGiles]

Has anyone actually got that sustain to work? I certainly was unable to.
Stephen