An implanted medical device (e.g. infusion pump) and an external device communicate with one another via telemetry messages that are receivable only during windows or listening periods. Each listening period is open for a prescribed period of time and is spaced from successive listening periods by an...http://www.google.de/patents/US6733446?utm_source=gb-gplus-sharePatent US6733446 - Ambulatory medical apparatus and method using a telemetry system with predefined reception listening periods
