Abstract: Systems, devices, and techniques for establishing communication between two medical devices are described. In one example, an implantable medical device comprises communication circuitry, therapy delivery circuitry, and processing circuitry configured to initiate a communication window during which the implantable second medical device is capable of receiving the information related to a cardiac event detected by a first medical device, the communication window being one of a plurality of communication windows defined by a communication schedule that corresponds to a transmission schedule in which the first medical device is configured to transmit the information, control the communication circuitry to receive, from the first medical device, the information related to the cardiac event that is indicative of a timing of the cardiac event with respect to a timing of the communication window, schedule and control delivery of a therapy according to the information related to the cardiac event.

Abstract: A retractable cover for closing an opening in a substantially flat surface. The cover has particular application for closing the oil change pit in the floor of a vehicle service facility. The cover comprises a plurality of stacked flat members, each of the flat members being provided with a clasper for engaging the flat member which is stacked therebelow as well as a wheel for engaging a track for guiding the extension of flat members from a first, retracted position in which the flat members are stacked directly above each other to allow access to the opening to a second, extended position in which the flat members are stacked in staircase fashion to cover the opening. Each of the flat members is provided with a stop for engaging the flat member stacked therebelow to retain the flat members in engagement with each other when extended to the second position.