This type of door must be unlocked before it can be operated.
Locked Door with Access Card
Construct any type of door so it functions in the game. Place an L[0,Channel] in the door sector. Then place an Access Switch (#130 or #170) tagged [ActivationSound,Channel], and an Access Card (#60) somewhere in the map. A value of 212 is the standard choice for ActivationSound. You can change the colours of the Access Switch and Card by adjusting their palettes: [0] = blue, [21] = red, or [23] = yellow.
Locked Door with Switch
Construct any type of door so it functions in the game. Place an L[0,Channel] in the door sector. Then place a Switch somewhere in the map and tag it [ActivationSound,Channel]. If you don't specify a value for ActivationSound, a preset sound will be used.
Locked Doors with Touchplates
Construct any type of door so it functions in the game. Place an L[0,Channel] in the door sector. Then place a T[NumberOfActivations,Channel] in your Touchplate sector. NumberOfActivations is the number of times the door will unlock/lock when you step on the Touchplate (0 being infinite). If you choose to use NumberOfActivations, make sure the player doesn't end up permanently locked out.