NEC NEAX 2400 IPX Manual page 173

POST INSTALLATION TEST
SDT Card Loopback Test
STEP 2: Make sure that the "LPB" lamp on the PA-SDTA card, or the "SYCxx" lamp on the PA-SDTB card
lights steady-green.
STEP 2.5: When the loopback pattern is "local loopback," confirm that the "OPT" and "SYNC" lamps are both
OFF on the PA-SDTA card.
("OPT" and "SYNC" lamps are OFF = Result of loopback test is fine)
STEP 3: Return the key settings of the P-SW key (on PA-SDTA card: see
CHAPTER 6
Page 158
Revision 1.0
NDA-24299
Figure 6-15) to the original position.