Where is the switch activating the interior lights when a door is opened?

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I want to add a red LED light strip on the outer edge of each door...the aspect exposed when the door is open…where the latch is located. I want these red lights to illuminate with the interior lights when a door is opened...to make open doors highly visible to street bicyclists at night. Easy to wire if I can tap into the switch or activator wiring but where is the switch? No visible spring-loaded button switch anywhere on the door frame. So, where is the switch?