by the path 506 if the degraded mode option is present the cpu reads the system code on the magnetic card in the reader slot via the card reader coils 74 and then reads the switches 140 in fig4 the cpu 66 compares the system code on the card to the system code on the switches for a match this comparison is symbolized by the block 508 in fig1 if there is no match the cpu 66 turns on the red led for a time set by the switches on the switch and relay board 62 in fig2 this indicates no authorization as symbolized by the state 510 the cpu 66 then addresses the feature memory 98 to determine if the no go option is in effect as symbolized by the state 512 if it is not in effect the cpu 66 returns to the background loops 443 via the path 514 if the option is in effect the cpu addresses the no go relay 166 in fig4 through the driver 70 by placing the proper address on the lines 172 and writing a logic 1 on the buffered d 0 data bit line 68 the no go relay 166 is thereby energized for a time set by the switches on the switch and relay board 62 and whatever external device that is coupled to the no go relay contacts through the lines 167 will be signalled that an unauthorized person has attempted an entry.