[GLLUG] An obscure VOIP problem

Chris Bell chrisbell at chrisbell.org.uk
Sat Oct 8 16:38:01 UTC 2022

My sister has direct FTTH with an Analogue Telephone Adapter provided by 
CommunityFibre.co.uk. She has dynamic IPv4 and dynamic IPv6 addresses.
Almost everything works fine except when dialling a telephone number that 
requires a subsequent button press to select the required service. This always 
works or always fails, depending on the destination.
She has a new Siemens Gigaset C570HX handset, C575A DECT base station, plus a 
pre-configured Grandstream HT801 Analogue Telephone Adapter (ATA) supplied by 
CommunityFibre.co.uk. There is a continuous internet data link from the ATA 
indicated by flashing LED's, but I do not know how the system sends the 
original DTMF. There is a suggestion that the DTMF might be converted and sent 
as digital codes by the ATA instead of audio tones, and converted back before 
being passed on to the current Public Service Telephone Network (Plain Old 
Telephone System, POTS), and might suffer corruption if the original DTMF is 
not completely removed first. The Siemens Gigaset equipment probably meets the 
precise DTMF requirements, but I have no control over the current VOIP system 
or the destination PABX.
We are both long since retired and would prefer not to pay much higher charges 
for a business class connection, but I may have to choose a different VOIP 
supplier who can still retain her original telephone number.
Any information and suggestions welcome. Thanks.
Chris Bell
Website chrisbell.org.uk

More information about the GLLUG mailing list