In order to prevent damages on SDB1 due to powerful beams coming from the aligned CITF, a protection has been implemented in PR and SR DSPs. First of all, the  alignment procedure for PR and SR has been changed, and it is mandatory to use only the new one, otherwise the protection will not work. PLEASE, DO NOT ALIGN PR AND SR IF YOU ARE NOT SURE OF WHAT YOU ARE DOING.

The main change is the introduction of a switch (gNAME: MAR_TY_ALI), which is supposed to have value 0 or 1. If 0, PR/SR is moved to the supposed parked position. If 1, PR/SR is moved to the supposed aligned position. The true aligned position can be found in the usual way, only after setting the switch to 1. At this point, one can find that a small refinement has to be done, and he can change the usual gNAMEs MAR_TX_SET, MAR_TY_SET. At the end, the good setting must be kept up to the next refinement, and not changed for any other reasons. If the mirror has to be parked, it must be done using the switch. No other condition is allowed, but the aligned and the parked ones. In the procedure used to refine the alignment, one can temporarily misalign as usual the mirrors by 10 urad, and this is not dangerous.

The protection consists in the fact that, when PR is in the aligned state, if SR crosses for any reason a 'forbidden region', PR is quickly sent to the parked state, avoiding flashes in the central cavity. Currently the forbidden misalignement for SR, both TX and TY, is from 15 urad to 400 urad. The protection acts on the switch, putting it at zero, and obviously it does nothing if the switch is already at zero.