An orthotic device includes a rigid support member and a removable inner liner having a contact surface adjacent the support member formed of a non-skid or non-slip material. The apparatus preferably are of a modular design, and are especially useful for playground or similar equipment. The staple fiber batt material is includes between 20% to 100% by weight of a regenerated cellulosic staple fiber material, such as rayon, and from 80% to 0% by weight of a polymeric staple fiber, such as nylon. The flow fins of at least one of the first or second sets thereof are tapered from enlarged ends of the fins to reduced ends thereof for forcing liquid adhesive material between the interface surfaces longitudinally of the fins from the enlarged ends thereof toward the reduced ends thereof automatically when the interface surfaces are brought together. The base station separates the combined signal to recover the digital portion and the analog portion and employs the analog portion to convey communicated information and the digital portion to control frequency hopping in the transmitter of the base station.