AM64/128A User Manual
The function of the links is as follows:
J1 Transmission disable
This link is always left in position
J11 Watch dog enable
This link is always left in position
J21 This connects the supply earth to the circuit ground in position
The circuit ground is floating in position
WARNING
Only authorised personnel can be allowed to open the Line Terminat ing Unit case to change the link settings. Misuse or any modifications carried out to this unit other than in accordance with the instructions supplied, will in validate both the guarantee and CE approval.