When you set the Receive Mode to Fax/Tel Mode, if the call is a fax, your machine will automatically receive it. However, if it is a voice call, the machine will sound the F/T ring (fast double-ring) for the time you set in the F/T Ring Time option. When you hear the F/T ring, it means that a voice caller is on the line.
The F/T Ring Time feature works when you set Fax/Tel Mode as the Receive Mode.
Because the F/T ring is made by the machine, extension and external telephones will not ring; however, you can still answer the call on any telephone.