Above you'll see an early kiosk notice for exchanges 'with dialling tone and where the Operator was accessed by dialling '0'. ' Not all early exchanges had dialling tone - I have an old GPO exchange that served a village in Northumberland from the late 1920's until 1950 and that doesn't have a dialling tone and the operator was accessed by dialling '01'. Also it doesn't have the usual 'double beat' ringing but the single beat ring not unlike the American ringing.
Many thanks to Ian Jolly for this information.
