Voice Services ->SPx Service -> DefaultRing: 2
Ring Settings -> Ring Profile A -> Ring Pattern 2: 60;(0+60)
The default ring pattern (pattern 1) is: 60;(2+4)
Ring for 2 seconds, silence for 4 seconds and repeat.
Now it's ring for zero seconds and silence for 60, allowing you to answer the call.
Edit:
This is how I did it on one of my phones:
Ring Settings -> Ring Profile A -> Ring Pattern 2: 60;(.4+60)
1 short ring then silence.