to be the inventor of the E-meter, a claim which is in keeping with the Scientology stance that Hubbard is the "source", or "the only originator of all Dianetics and Scientology material". The E-meter was not part of the early days of Dianetics and Scientology. Auditing was composed of conversation and not led by a mechanical device. Hubbard introduced an E-meter prototype during the 1952 Philadelphia Doctorate Course but did not introduce his transistorized version until several years later. The E-meter became "the principal material artifact" of Dianetics and Scientology from the 1960s onward. In the book, L. Ron Hubbard, Messiah or Madman?, Bent Corydon wrote: Though it seemed for a while that Scientology's more advanced techniques would serve without an E-meter, a few months later in May 1955, Hubbard wrote: The Scientology meter was smaller, based on transistors rather than vacuum tubes, and powered by a low-voltage rechargeable battery rather than line voltage. From then on, the E-meter was a required tool for Scientology ministers. The "Hubbard Mark II" E-meter was christened in 1960 and the Hubbard Mark III shortly after. On December 6, 1966, Hubbard won a patent on the Mark V version under the name "Hubbard Electropsychometer". Corydon wrote that the Hubbard E-meter was actually developed by Scientologists Don Breeding and Joe Wallis, though the patent () does not list other developers. Corydon's account was said to be based on the memoirs of Hubbard's son, Ronald DeWolf, but in 1987, DeWolf sued the publisher to prevent publication and swore an affidavit repudiating everything in the book. The Scientology E-meter has been redesigned and re-patented several times since its first introduction to Dianetics (e.g.: , , ). In 1969, Scientology was accepted as a religion by the Court of Appeal and declared that the E-meter was useful in "bona fide religious counseling". District Court Judge Gesell, while denying medical validity to the device, returned the e-meter to the Church. All e-meters from this point forward had to be inscribed with a disclaimer that it was not for medical or scientific diagnoses, treatment or prevention of any disease. The church reformulated the disclaimer into: "The Hubbard electrometer is a religious artifact. By itself, this meter does nothing. It is for religious use by students and Ministers of the church in Confessionals and pastoral counseling only." Modern applications EDA meters are used in both therapist-patient and bio-feedback settings. EDA is