The first successful pacemaker was developed in 1952 by Paul Zoll (1911–1999) in Boston, in collaboration with the Electrodyne Company. The device was worn externally on the patient’s belt. It relied on an electrical wall socket to stimulate the patient’s heart through two metal electrodes attached to the patient’s chest. Wilson Greatbatch, working together with Earl Bakken, developed an internal pacemaker. It was first implanted by the surgeons Dr. William Chardack and Dr. Andrew Gage in 1960.