I wasn’t attempting to give a visual representation of the ringing current the PSTN switch delivers for a call made to a call sign number, I was simply trying to show what ringing cadence is…., suffice to say the phone instrument makes two different noises depending on what number was called ( the directory number or the call sign number ) something that some may not be aware of , as said , call sign was a pretty niche facility anyway, that many if not most would be unaware of.
Call facilities come and go , one that you find useful is not ( currently ) being retained in the change to a VoIP based phone system, if its removal were a deal breaker , obviously you could change provider that supports that facility ( if one exists )
I don’t recognise your assertion that BT have said ‘nothing will change’ with the advent of DV , there are many things that won’t exist when all telephony is VoIP , however , in its basic form, the ability to make and receive calls is unchanged with DV.
The fact that a facility is being removed ( something that could have been removed irrespective of the call platform , if BT decide it’s not worth continuing with ) is just business ….no company guarantees that every feature or product in their portfolio will be available for ever, and if it’s something not worth continuing with , then ( unfortunately ) that’s it, I don’t really know what other answer you expect.
