Is it possible to differentiate the tones used by the Video door entry system for calls originating from the outdoor station and the doorbell?

Yes, it is possible. To associate calls from the doorbell and the outdoor station with different tones, use terminal 9 of the 16-pin connector and the dedicated voice line for the doorbell (terminal 2) Alternatively, this input can be used in a "Bell" configuration using an N.O. (normally open) button connected to terminals 9 and 5 of the 16-pin connector, and setting the correct type of doorbell.