Acer 505 series - Manual (Page 14)

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Modem notice
This equipment has been approved to Council Division 98/482/EC - “CTR 21” for
pan-European single terminal connection to the Public Switched Telephone
Network (PSTN). However, due to differences between the individual PSTNs
provided in different countries, the approval does not, of itself, give an
unconditional assurance of successful operation on every PSTN termination point.
In the event of problems, you should contact your equipment supplier in the first
instance.