Busch-Jaeger Busch-Wachter DualLINE 6813/11 Series Operating Instructions Manual page 51

Constant light control in big rooms with memory control unit 6550 U-101,
extension unit 6805 U and normally-open contact button, for fluorescent lamps.
If more than 2 extension units 6805 U are used, the pushbutton
operation may be affected.
6805 U 6550 U-101
Slave Master
11 ENG
Fig. 8