The above diagrams represent the P/E, RNG, and PEN logic during a test with all guard vetoes disabled. The equations for P/E, RNG, and PEN events are:
Event type |
Coincidence equation |
P, E |
P1.P2.P4* |
RNG |
P1.P2.P4 |
PEN |
P1.P2.P8 |
The buffers into which "orderly" events can fall are as follows:
Range |
No guards triggered |
Low, not high guard triggered |
High guard triggered |
P1 |
NONE |
NONE |
NONE |
P1 through P2 |
P/E |
P/E |
P/E |
P1 through P3 |
P/E |
P/E |
P/E |
P1 through P4, P5, P6, or P7 |
RNG |
RNG |
RNG |
P1 through P8 |
RNG, PEN |
RNG, PEN |
RNG, PEN |
In order to test whether the P3 center/guard crosstalk problem could cause the high guard threshold to trigger as well as the low guard threshold, all guard vetoes were removed from the P, E, RNG, and PEN equations. This was not the case, so PET was returned to the previous state for most of 1993. Note that this period, however, is the only time before the current command state was implemented when a penetrating event that triggered a guard threshold would be handled in an unbiased manner, such that it would be counted in the PEN rate if and only if it was eligible for output as a PHA event (in the state implemented on 99014, the reverse bias is applied, and the PEN rate rejects more events than the buffers).
new 6 August 1999, revised 30 April 2000