Does the door open automatically when the call is answered? Is the device off the FXS port smart enough to notice when the call is connected, that the door should be opened? Or does a code need to be sent to the device after connect?
Note that without getting super fancy, the 'answer' button on the phone will only always do just that--answer an inbound call that is presented to it.
You assign an extension to an analog phone in CME in one of two ways. The first is a simplier config, and will work just fine for you, I think.
* Non SCCP controlled (FXS port will not have supplmentary services):
dial-peer voice 23 pots
port 0/0/0
destination-pattern 1001
* SCCP controlled (conference/hold/transfer/hookflash features supported):
dial-peer voice 23 pots
port 0/0/0
service stcapp
ephone-dn 10
number 1001
ephone 10
mac
type anl
button 1:10