where even the appropriate adapter cable CBB01 is added. To select suitable heatset, Sennheiser provides a menu. Basically, however, the question arises whether it makes sense to choose a heatset which is significantly more expensive than the FritzFon itself. Since I have a hearing loss, but to me this is worth. Even better is the way the SC 660, which exhibits a frequency dynamics on the listeners to 18,000 Hertz. So can thus be heard music. The 4 stars here because of the low dynamics, (6.800) which, however, to make phone calls is fully sufficient. Both devices are working on iPhon, iPad and iMac.