Systems and methods for communicating between medical devices. In one example, an implantable medical device comprising may comprise one or more electrodes and a controller coupled to the electrodes. The controller may be configured to receive a first communication pulse at a first communication pulse time and a second communication pulse at a second communication pulse time via the one or more electrodes. The controller may further be configured to identify one of three or more symbols based at least in part on the time difference between the first communication pulse time and the second communication pulse time.