Philips Support
What is FSK/DTMF and why do I need it?
FSK (Frequency-Shift Keying) and DTMF (Dual Tone Multi-Frequency) are data transmission formats that carry caller information.
The information on this page applies to the following models: M6651WB/05 , D6351B/38 , XL4951S/FR . Click here to show more product numbers ›