I'm not sure that you can actually change the ring cadence on this model, other than between the pre-defined ringtones included.

However you can upload custom ringones, so you could make one with the loop time set to match the cadence you desire. I think would probably work.

The free audio software 'Audacity' can be used to generate and mix tones together into your desired pattern.

audacityteam.org

I have a question regarding the W60B also, I have a client with a W56H connected to a W60B phone that sometimes doesn't ring when its on the base is this a known bug?