On multiple unit trains, the guard uses a buzzer code to communicate with the driver. Once the doors have closed and platform duties are complete, the guard informs the driver by sending the signal for "ready to start", which is two rings (hence "ding-ding"). There was a debate whether guards should only give the "ready to start" or station staff the "right away" signal if the platform starting signal was clear.
On multiple unit trains, the guard uses a buzzer code to communicate with the driver. Once the doors have closed and platform duties are complete, the guard informs the driver by sending the signal for "ready to start", which is two rings (hence "ding-ding"). There was a discussion about whether guards should only give the "ready to start" or station staff the "right away" signal if the platform starting signal was clear.