The present invention relates to hydrogenated nitrile rubber polymers having lower molecular weights and narrower molecular weight distributions than those known in the art. The group call service server receives a floor request from a requesting user equipment unit included in the group, and handles the floor request based on a media type associated with the floor request. In addition, various embodiments of the present invention are directed to an infant support control device configured to impart soothing sensation to a child positioned in the infant support.