Patent ID: 8024043

Claim:
A telemetry system for enabling radio-frequency (RF) communications between an implantable medical device and an external device, comprising: an antenna, an RF transmitter, an RF receiver, and a controller incorporated into each of the implantable and external devices; a wakeup timer incorporated into the implantable device wherein the RF transmitter and receiver are interfaced to the controller in the implantable device to enable the RF transmitter and receiver to be powered up or down; wherein the external device is programmed to transmit a data segment containing a repeating sequence of special wakeup characters in order to establish a communications session with the implantable device; wherein the implantable device is programmed to power up its transmitter and receiver for a specified time window at periodic intervals defined by the wakeup timer and wait for receipt of one of the special wakeup characters transmitted by the external device; wherein the implantable device is programmed to maintain its transmitter and receiver in a powered-up state upon receipt of a special character and for as long as consecutive special wakeup characters continue to be received, to transmit an acknowledge signal to the external device upon receipt of at least one character other than a special wakeup character, and then to wait a specified period of time for a response from the external device; wherein the wakeup special character is bit balanced; and, wherein the external device and the implantable device are programmed to establish a communications session when a response to the acknowledge signal is received by the implantable device.