In Smith v. Maryland, 442 U.S. 735 (1979), the Supreme Court applied the reasonable expectation of privacy test to the question of whether the government's warrantless installation and use of a pen register installed in the telephone company's offices in order to record telephone numbers dialed from Smith's telephone was a Fourth Amendment search. The pen register was used to discover that a telephone in Smith's home had been used to place a telephone call to a robbery victim who had received threatening calls. The Supreme Court held in Smith that there was no Fourth Amendment violation because Smith did not have an expectation of privacy in the telephone numbers dialed from his telephone, which were voluntarily transmitted to the telephone company. Id. at 742-44. The Court concluded that all subscribers realize that the telephone company has facilities for making permanent records of the numbers they dial, which they see on their monthly bills. Id. at 742. The Court further held that even if Smith had an expectation of privacy in the numbers dialed from his home telephone, it was not an expectation that society was prepared to recognize as reasonable because "a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties." Id. at 743-44. Thus, to date, installation and use of a pen register simply to record the numbers dialed from a specific telephone is not subject to Fourth Amendment requirements. In Smith, the Supreme Court concluded that the installation and use without a search warrant of a pen register--a device that makes a record of numbers dialed on a telephone--did not violate the Fourth Amendment. Id. at 745-46. The Court reached this conclusion based on its determination--under an analysis derived from Katz v. United States, 389 U.S. 347 (1967)--that Smith had neither a subjective expectation of privacy nor an objectively reasonable expectation of privacy regarding the numbers he dialed. Smith, 442 U.S. at 742-43. As to the subjective expectation of privacy, the Supreme Court observed that it doubted "that people in general entertain any actual expectation of privacy in the numbers they dial." Id. at 742. The Court reasoned that "all telephone users realize that they must 'convey' phone numbers to the telephone company, since it is through telephone company switching equipment that their calls are completed" and that they also realize "that the phone company has facilities for making permanent records of the numbers they dial." Id. In short, the Supreme Court concluded that "it is too much to believe that telephone subscribers . . . harbor any general expectation that the numbers they dial will remain secret." Id. at 743. In connection with this point, the Court observed that "the fact that Smith dialed the number on his home phone rather than on some other phone could make no conceivable difference, nor could any subscriber rationally think that it would." Id. As to the existence of an objectively reasonable expectation of privacy, the Supreme Court stated that "even if petitioner did harbor some subjective expectation that the phone numbers he dialed would remain private, this expectation is not 'one that society is prepared to recognize as "reasonable."'" Id. The Court rested its conclusion on what is known as the third-party-disclosure doctrine. Id. at 743. The Court pointed out that it "consistently has held that a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties." Id. at 743-44. In particular, the Court discussed its decision in United States v. Miller, 425 U.S. 435 (1976), which held that bank depositors have no legitimate expectation of privacy regarding financial information provided to a bank. See Smith, 442 U.S. at 744. The Court observed that "because the depositor 'assumed the risk' of disclosure" in providing information to the bank, "the Miller Court held that it would be unreasonable for him to expect his financial records to remain private." Id. The Court, therefore, determined that the third-party-disclosure doctrine negated any legitimate expectation of privacy regarding the numbers dialed on a telephone: "When he used his phone, petitioner voluntarily conveyed numerical information to the telephone company and "exposed" that information to its equipment in the ordinary course of business. In so doing, petitioner assumed the risk that the company would reveal to police the numbers he dialed. The switching equipment that processed those numbers is merely the modern counterpart of the operator who, in an earlier day, personally completed calls for the subscriber." Id.