According to this thread:
Hi all, Does anyone have a list of what the bell/buzzer codes are? I've seen a list on a 377 inside the door panel, but can't remember them. I know 1 is stop, 2 is right away and 9 is emergency but cant remember the rest. taa, James.
www.railforums.co.uk
buzzer code 3-3-1 is "release central door locking", so I assume that would be used in both types of unit?
No, it’s never used and forgot that even it exists until you reminded me. I guess it technically could be used but the guard would always phone you or if they were close enough to the front, they would just knock on your window. To be honest, if a guard did that, I think there would be some very confused drivers
Alternatively, on the Class 22x, the microphone (by the door) and the speaker (in the cab) automatically turns on when the guard puts his/her key in so you can hear everything- e.g. the guard and the customer host having a chat; unfortunately for a lot of customer hosts and some guards, I don’t think many of them realise that we can hear exactly what they’re saying including if they’re having a moan about the driver!
So if the guard wants the doors to be re-released, it’s far easier to just say “Please open doors again driver” rather than having to use the phone or knock on the driver’s door.
On the subject of release central door locking- the Class 180s had something like that which, at least to me, seems like a very bizarre set up. When you stop at a station, I think the driver has to kind of ask permission from the guard before releasing doors. So you would hear a series of buzzes between Driver/guard before the doors are released. I believe it was 2-2 driver to guard and then 2-2 guard to driver and then the driver would release doors. I’m not 100% on this so perhaps someone could shed some light on this.