What is it?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
From internet:

CdS cell output photocoupler Classic
MCD5221

Useful for creating such as AGC circuit.

Resistance value between the output side of the CdS cell current flows to the input side of the LED changes. Where the output is resistance rather than a constant current is miso (relation between voltage and current is linear).

Some discontinued direction because photo coupler of CdS output is using harmful Cd (cadmium). There is for now no element to the same function without using harmful substances. Can be re-design the circuit from the root to the circuit without a photo coupler of CdS output but circuit becomes complicated.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.