INADVERTENT ACTIVATION OF THE STANDBY PWR SWITCH WHEN THE INTENTION WAS TO RELEASE THE LOCK ON THE REINFORCED COCKPIT DOOR CAUSED THE AUTOPLT TO DISCONNECT RESULTING IN AN ALT EXCURSION WHICH WAS NOT NOTICED BECAUSE OF THE CONFUSION OF BEING PRESENTED WITH VARIOUS WARNINGS ALSO CAUSED BY THE PWR LOSS.

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ALTDEV. AUTOPLT TRIPPED OFF WHEN CAPT INADVERTENTLY SWITCHED STANDBY PWR SWITCH OFF; WHILE REACHING FOR THE NEW DOOR UNLOCK SWITCH. THE DOOR UNLOCK SWITCH AND STANDBY PWR SWITCH ARE LOCATED ADJACENT TO ONE ANOTHER AND LOOK AND OPERATE THE SAME. WHEN AUTOPLT TRIPPED OFF; ACFT CLBED 400 FT MAX BEFORE CAPT RETURNED ACFT TO LEVEL FLT AT FL340. NO OTHER ACFT WAS IN THE VICINITY VIA TCASII. CTR MADE NO COMMENTS ON ALTDEV. OTHER FACTORS: COPLT WAS RETURNING TO COCKPIT AND CAPT WAS ANSWERING RADIO CALLS AT SAME TIME. CORRECTIVE ACTION SHOULD BE TO MOVE THE LOCATION OF THE NEW DOOR OPEN SWITCH WHICH WAS INSTALLED AS A RESULT OF THE NEW SECURITY DOOR INSTABILITY. IT'S POS RESULTED IN TURNING STANDBY PWR SWITCH OFF; WHICH TURNED OFF AUTOPLT; ALLOWING ACFT TO CLB SLOWLY BEFORE PLTS SENSED CLB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE SWITCHES INVOLVED ARE ON THE OVERHEAD PANEL; ONE ABOVE THE OTHER; NO MORE THAN 1-2 INCHES APART. THEY ARE IDENTICAL IN DESCRIPTION AND OP. THERE IS A COMPANY BULLETIN WARNING OF THE POSSIBILITY OF UNINTENDED ACTIVATION AND THERE HAVE BEEN SEVERAL INCIDENTS AT THIS COMPANY. AS A RESULT THERE IS A PROGRAM IN PLACE TO INSTALL A GUARD FOR THE STANDBY PWR SWITCH TO PREVENT UNINTENDED ACTIVATION.