Zoomlion Limit Switch/A2B Switch 1020500007,1020500721.
It's used in Zoomlion cranes QY12D431.3、QY16H431.1、QY16D431.2、QY20H431.5、QY20V441、QY20D431.2、QY25V431.2、QY30V532.3、QY40V532.1、QY70V533.5、QY100H-3、QY130V633、QY180V633、QY220V633, etc.
The anti-two-block switch monitors the hook block and its relationship with the head of the boom.