In my SE120 the console card is installed in Ports 2-3 of shelf 4, which is the 96 port shelf on the left hand side of the bottom shelf that also has the CPU in it.
ports 2-3 is slot 2, counting from the right.
The LEND command (list Equipment Number Details) reveals that the data base does indeed specify a console card in that slot
? LEND 305 308
EN PORT-TYPE DN/TN
305 SPARE
306 CONSOL 398 D
307 CONSOL 398 D
308 SPARE
309 SPARE
310 SPARE
?
A diagnostic test of type 16 on port 306 reveals
? EDT 16 306
VALUE 1
TEST ABORTED - CONSOL DEACTIVE
?
A list port status command
? LPS 306
EN PORT-TYPE STATE MANBUSY
306 CONSOL 00 00
? LPS 307
EN PORT-TYPE STATE MANBUSY
307 CONSOL 00 00
A list extension attributes reveals
? LEXA 0 398
SECOND PILOT DN MEMBER OF PSC REC MASTER ACTIVE/
EXTN EXTN OF GROUP PICK-UP GROUP ENABLED ANN EXTN MANBSY
398 CONSOLE DN
A list group attributes reveals
? LGA
GROUP TYPE HUNT MODE DN ACCESS FAIL_PT CARD PORT
80 CONSOLE CYCLIC 320G
A list group member ship reveals
? LGM 80
CONSOLE GROUP 80 CYCLIC
NO. EN
0 306
*************** END OF RECORD ***************
To add a new console use
The new console to be added should be switched off until NCON and REG have been executed
NCON PORT EXTN
PORT and EXTN must be SPARE before using NCON
REG GROUP MEMBER PORT
Where GROUP would be 80 in this setup ( may be 53 in 250c2)
where MEMBER would be 1 (ie next number after 0)
where PORT in the equipment number that was SPARE before the NCON command