Presently before the Court for review in this consolidated appeal are orders of the trial court suppressing evidence obtained by the Commonwealth via pen registers and telephone intercepts, as well as physical evidence subsequently seized pursuant to warrant. The trial court’s suppression orders were based upon the absence of a neutral determination that probable cause existed for the use of pen registers.
In December, 1982, on the basis of information which had been provided by confidential informants, the Commonwealth began an investigation into illegal gambling operations in Philadelphia. In January, 1983, Pennsylvania State Troopers received information from a confidential informant about an illegal numbers operation that was being conducted in Philadelphia through telephone number (215) 271-7078. Records maintained by Bell Telephone Company of Pennsylvania revealed that this number had been assigned to the defendant, Richard Mastro, at Vollmer Street, in Philadelphia. A dialed number recorder (DNR) was installed on this telephone pursuant to an order entered on January 6, 1983 by the Honorable Michael J. Conroy of the Municipal Court of Philadelphia.1 In subsequent orders entered on February 25, March 25, and May 24, 1983, Judge Conroy authorized the continued use of the DNR on Mas-tro’s telephone for additional thirty day periods.
*433In February, 1983, law enforcement officers received further information from a second confidential informant that illegal sports bookmaking was being conducted by a man referred to as “Nick” at telephone number (215) 336-8460. Records maintained by Bell Telephone Company showed that this number had been subscribed to by defendant, Nicholas DeStefano, at 2438 Juniper Street in Philadelphia. On February 17, 1983, law enforcement officers obtained an order from Judge Conroy authorizing the installation of a pen register on DeStefano’s telephone for a period of thirty days. This authorization was extended for additional thirty day periods by orders dated March 17, April 14, and May 4, 1983.
Information obtained through the pen register installed on Mastro’s telephone disclosed a pattern of telephone calls made from Mastro’s telephone to another telephone and transferred through call forwarding to telephone number (215) 389-8903. Bell Telephone Company’s records revealed that this number had been subscribed to by Jerry DiJo-seph,2 located at 1604 South Clarion Street in Philadelphia. On March 4, 1983, Judge Conroy authorized the installation of a pen register on DiJoseph’s telephone. Additional thirty day extensions were authorized on March 30 and May 4, 1983.
Based upon information obtained through these pen registers and through additional confidential informants and corroborated by independent police investigation and surveillance, law enforcement officials obtained authorization from the Honorable J. Sydney Hoffman of the Superior Court to install wiretaps on the telephones of Messrs. Mastro, DeStefano and DiJoseph. These wiretaps were installed on April 15, 1983. Interception of the telephone calls made on Mastro’s and DeStefano’s telephones terminated on April 26, 1983. Interception of DiJoseph’s telephone conversations continued until May 4, 1983.
*434The investigation continued, and on May 9, 1983, law enforcement officials obtained search warrants for twenty-three locations, including the residences of each of the eight defendants. Pursuant to these warrants, the police seized physical evidence of corrupt organizations and illegal gambling. The eight defendants were arrested on December 8, 1983, and were charged with conspiracy, corrupt organizations and related offenses. The cases were consolidated on August 1, 1984.
All of the defendants filed pre-trial motions to suppress the evidence which had been obtained pursuant to the pen registers and wiretaps, as well as the physical evidence which had been seized pursuant to the search warrants. A hearing was held and, on September 17, 1984, the suppression court suppressed the evidence which had been obtained pursuant to the Mastro pen register. A decision regarding the remainder of the evidence sought to be suppressed was delayed until briefs could be submitted by the parties. On October 29, 1984, the suppression court ordered that this remaining evidence also be suppressed. On April 18, 1985, the suppression court filed formal findings of fact and conclusions of law.
In Commonwealth v. Beauford, 327 Pa.Super. 253, 269, 475 A.2d 783, 791 (1984), appeal dismissed, 508 Pa. 319, 496 A.2d 1143 (1985), a panel of this Court held that Article 1, section 8 of the Pennsylvania Constitution prohibited the installation and use of pen registers without a warrant issued upon probable cause. The Court rejected the reasoning of the United States Supreme Court in Smith v. Maryland, 442 U.S. 735, 99 S.Ct. 2577, 61 L.Ed.2d 220 (1979), which had earlier held that the use of a pen register was not a search under the Fourth Amendment of the Constitution of the United States. The Commonwealth contends in the instant appeal that the suppression court erred when it applied the Beauford requirement of probable cause retroactively to the pen registers which had been used in the instant case because these pen registers had been installed prior to the date on which Commonwealth v. *435Beauford, supra, was decided. We are constrained to disagree. “[W]here an appellate decision overrules prior law and announces a new principle, unless the decision specifically declares the ruling to be prospective only, the new rule is to be applied retroactively to cases where the issue in question [has been] properly preserved at all stages of adjudication up to and including any direct appeal.” Commonwealth v. Cabeza, 503 Pa. 228, 233, 469 A.2d 146, 148 (1983). The Beauford court did not declare its ruling to be prospective only; and in the case sub judice, the issue of lack of probable cause has been properly preserved for review at all stages. Therefore, the Beauford rule is applicable to the facts of the instant case.
The Commonwealth also contends that only those defendants upon whose telephones the pen registers were installed have standing to challenge the evidence obtained from the pen registers. However, in Commonwealth v. Beauford, supra, this Court suppressed evidence which had been obtained through the use of pen registers as to each of six defendants despite the fact that all defendants had not had a pen register installed on their telephones. In rejecting the decision of the United States Supreme Court in Smith v. Maryland, supra, the Court said: “[W]e do not hesitate to say that a caller and the person he calls expect and are entitled to as much privacy in the fact that they are talking to one another as in what they say to each other.” Commonwealth v. Beauford, supra 327 Pa.Super. at 266, 475 A.2d at 789 (emphasis added). From this we conclude that all defendants in the instant case have standing to challenge the evidence obtained through the pen registers which were installed on the telephones of Messrs. Mastro, DeStefano and DiJoseph.
The matter of probable cause was considered by this Court in Commonwealth v. Doty, 345 Pa.Super. 374, 498 A.2d 870 (1985). There we said:
The standard for determining whether probable cause existed [for a wiretap or a pen register] is the same as that used to determine cause for search warrants. See: *436United, States v. Talbert, 706 F.2d 464, 467 (4th Cir.1983); United States v. Falcone, 505 F.2d 478, 481 (3d Cir.1974), cert. denied, 420 U.S. 955, 95 S.Ct. 1338, 43 L.Ed.2d 432 (1975). The facts contained in the affidavit for a search warrant must be such that an independent, issuing authority, exercising reasonable caution, can conclude that the items sought are connected with criminal activity and that they will be found in the place to be searched. Commonwealth v. Council, 491 Pa. 434, 443, 421 A.2d 623, 627 (1980); Commonwealth v. Ryan, 300 Pa.Super. 156, 167, 446 A.2d 277, 283 (1982). Similarly, in an application for a wiretap [or a pen register], the Commonwealth must establish probable cause to believe that (1) a person has or is about to commit one of the offenses enumerated in the statute, (2) that communications [or information] relating to that offense will be transmitted, and (3) that such communications [or information] will be intercepted on the facility under surveillance. See: United States v. Armocida, [515 F.2d 29, 35 (3d Cir.), cert. denied sub nom., Conti v. United States, 423 U.S. 858, 96 S.Ct. 111, 46 L.Ed.2d 84 (1975) ].
Id., 345 Pa.Superior Ct. at 397-398, 498 A.2d at 882.
“[P]en register applications must [also] comply with Pa.R. Crim.P. 2003(a) and (b), which require that evidence establishing probable cause for issuance of a warrant appear in writing within the four corners of the affidavits submitted to the issuing authority ... [and be] ‘supported by oath or affirmation subscribed to by the affiant.’ ” Commonwealth v. Beauford, supra 327 Pa.Super. at 269 n. 7, 475 A.2d at 791 n. 7. As with all searches not falling within one of the recognized exceptions to the warrant requirement, a finding that probable cause exists must be made by a neutral judicial authority before a pen register can be installed.
The magistrate must make a judicial determination, albeit a nontechnical, common sense judgment ... as to whether probable cause exists. It is not enough for a policeman to present an affidavit to the magistrate prior to the *437search which affidavit the judiciary may consider on the issue of probable cause with complete hindsight after the police have completed their search. The magistrate must actually make a finding of probable cause to validate the warrant before he issues it. Moreover, he must do it by written order.
Commonwealth v. Chandler, 505 Pa. 113, 123-124, 477 A.2d 851, 856 (1984) (emphasis added).
In the instant case, the orders authorizing installation and use of pen registers were not based upon findings of probable cause. At the time when the applications for the use of pen registers were made, both the affiants and Judge Conroy were operating under the belief that a warrant based upon probable cause was not a necessary condition for the use of a pen register. It was for this reason that Judge Conroy made no findings before issuing orders authorizing installation of the pen registers in question. The orders do not suggest that Judge Conroy ever considered whether probable cause existed.
Moreover and in any event, the affidavits accompanying the pen register applications were insufficient to show the existence of probable cause. The affidavits in support of the Mastro and DeStefano pen registers contained vague and conclusory averments in support of the reliability of the tips received from the confidential informants; and police attempts to corroborate the information had been inconclusive. The affidavit in support of the installation of the DiJoseph pen register was based entirely upon information obtained through the Mastro pen register. Absent this information, the affidavit was void of facts showing probable cause.
Despite these errors which occurred in obtaining the prosecution’s evidence, the Commonwealth urges us to adopt the reasoning set forth by the Supreme Court in United States v. Leon, 468 U.S. 897, 104 S.Ct. 3405, 82 L.Ed.2d 677 (1984), and hold that evidence is not subject to suppression if law enforcement officials have acted in reasonable, good faith reliance upon authorization issued by a *438neutral magistrate but which later is found to be defective because unsupported by probable cause.
In United States v. Leon, supra, the United States Supreme Court examined the purposes of the exclusionary rule and determined that:
“The deterrent purpose of the exclusionary rule necessarily assumes that the police have engaged in willful, or at the very least negligent, conduct which has deprived the defendant of some right. By refusing to admit evidence gained as a result of such conduct, the courts hope to instill in those particular investigating officers, or in their future counterparts, a greater degree of care toward the rights of an accused. Where the official conduct was pursued in complete good faith, however, the deterrence rationale loses much of its force.”
Id. at 919, 104 S.Ct. at 3419, 82 L.Ed.2d at 696, quoting Michigan v. Tucker, 417 U.S. 433, 447, 94 S.Ct. 2357, 2365, 41 L.Ed.2d 182, 194 (1974). The Supreme Court concluded, therefore, that “suppression of evidence obtained pursuant to a warrant should be ordered only on a case-by-case basis and only in those unusual cases in which exclusion will further the purposes of the exclusionary rule.” Id. 468 U.S. at 918, 104 S.Ct. at 3419, 82 L.Ed.2d at 695 (footnote omitted). See also: Ex parte State v. Crittenden, 476 So.2d 632 (Ala.1985); State v. Anderson, 286 Ark. 58, 688 S.W.2d 947 (1985); Stabenow v. State, 495 N.E.2d 197 (Ind.App.1986); State v. Shannon, 472 So.2d 286 (La.App. 1985); State v. Sweeney, 701 S.W.2d 420 (Mo.1985); State v. Welch, 316 N.C. 578, 342 S.E.2d 789 (1986); State v. Wilmoth, 22 Ohio St.3d 251, 490 N.E.2d 1236 (1986); McCary v. Commonwealth, 228 Va. 219, 321 S.E.2d 637 (1984); Patterson v. State, 691 P.2d 253 (Wyo.1984), cert. denied sub nom., Spoon v. Wyoming, 471 U.S. 1020, 105 S.Ct. 2048, 85 L.Ed.2d 311 (1985). But see: People v. Bigelow, 66 N.Y.2d 417, 497 N.Y.S.2d 630, 488 N.E.2d 451 (1985); Polk v. State, 704 S.W.2d 929 (Tex.App.1986).
Suppression of the evidence obtained by the installation of the pen registers in the instant case cannot further *439the purposes of the exclusionary rule. At the time when the pen registers were installed, existing law explicitly told law enforcement officials that the use of pen registers did not constitute a search. Pursuant to the Constitution of the United States, according to Supreme Court interpretation, the use of pen registers did not require a prior showing of probable cause. See: Smith v. Maryland, supra. According to the law then in effect, therefore, law enforcement agencies were not required to obtain a court order or warrant in order to install and make use of a pen register. Nevertheless, in order to comply with telephone company requirements, police in the instant case went further than the law required and requested from a neutral magistrate an order authorizing installation of pen registers. The magistrate, who also acted pursuant to existing law, issued an order authorizing the use of pen registers without a showing of probable cause. It was not until later that the Superior Court, applying principles of state constitutional law, outlawed the use of pen registers without a prior showing of probable cause. It seems clear, therefore, that the use of pen registers by law enforcement authorities was accomplished in good faith, in accordance with statutory authority in the Commonwealth of Pennsylvania, and consistently with procedure explicitly approved by the Supreme Court of the United States. To suppress evidence obtained under these circumstances would not further any of the purposes intended to be served by the exclusionary rule. Indeed, to deprive the Commonwealth of the use of evidence obtained in good faith and in accordance with then existing law as determined by the highest court in the land, would not only fail to serve the purposes of the exclusionary rule but would tend to defeat a substantial public interest in law enforcement.3 Therefore, we agree with the Common*440wealth that an exception to the exclusionary rule must be created which has application narrowly to situations in which law enforcement officials have acted (1) in good faith; (2) in reasonable reliance upon a procedure expressly sanctioned by existing judicial decisions; and (3) pursuant to authorization obtained from a neutral magistrate. Because those prerequisites have been met in the instant case,'we reverse the orders suppressing the evidence obtained by the use of the pen registers.
We also reverse the order suppressing the evidence obtained through the telephone intercepts and the physical evidence seized pursuant to the search warrants. The suppression court’s order was based upon its conclusion that absent the pen register evidence, the affidavits in support of the wiretap applications and search warrants were insufficient to establish probable cause. However, in light of our holding that the pen register evidence should not have been suppressed, it was unnecessary to discount that evidence when determining the existence of probable cause.
Even without a “good faith” exception in this case, we would nonetheless be constrained to reverse that part of the order suppressing evidence obtained via wiretaps installed on the telephones of Mastro and DeStefano. Without evidence obtained through the use of pen registers on their phones, the affidavits in support of the Mastro and DeStefano intercepts were nevertheless sufficient to confirm the existence of probable cause. Both affidavits contained detailed information which had been provided to law enforcement officials by confidential informants. This information was sufficient to permit a reasonable person to conclude that Mastro and DeStefano had engaged in illegal gambling *441activities and were continuing to do so by using telephones located at their respective residences. The only question concerning these affidavits was whether the reliability of informants’ tips had been sufficiently established. We conclude that the reliability of the informants had been established.
“It is well settled that a 'tip’ from an unnamed informant can properly form the basis for probable cause provided there is adequate evidence of the informant’s credibility.” Commonwealth v. Miller, 334 Pa.Super. 374, 381, 483 A.2d 498, 501 (1984). See: Commonwealth v. Carlisle, 348 Pa.Super. 96, 100, 501 A.2d 664, 666 (1985).
In the Mastro affidavit, the existence of probable cause was based upon information which had been provided by three confidential informants. Two of the informants had admitted being numbers writers for an illegal gambling operation. They stated that they had placed bets regularly by dialing the telephone number which police traced to Mastro. Their involvement in the gambling operation provided them with a strong basis for knowledge. Moreover, the first informant’s reliability was adequately shown by the fact that he had previously provided law enforcement officials with information which proved to be reliable and accurate. See: Commonwealth v. Carlisle, supra; Commonwealth v. White, 311 Pa.Super. 146, 151-152, 457 A.2d 537, 539 (1983). The same is true with regard to the third confidential informant. Although the affidavit did not recite that the second informant had previously provided reliable information, the information provided by this informant was corroborated by the information obtained from the other two informants. Thus, it was worthy of consideration. See: Commonwealth v. Jones, 506 Pa. 262, 271, 484 A.2d 1383, 1388 (1984). Finally and most importantly, the statements of the informants had been against their penal interests and, therefore, could be found worthy of belief. See: Commonwealth v. Stickle, 484 Pa. 89, 97-98, 398 A.2d 957, 961-962 (1979); Commonwealth v. Neidig, 340 Pa.Super. 217, 222, 489 A.2d 921, 923-924 (1985); Common*442wealth v. Yacoubian, 339 Pa.Super. 413, 423-424, 489 A.2d 228, 233 (1985).
Similarly, the affidavit in support of the DeStefano wiretap application was based primarily upon information provided by a confidential informant. Not only was the informant involved in the gambling operation through his role as bettor and numbers writer, thereby establishing a strong basis for knowledge, but he had also provided law enforcement officials with information in the past which had proved to be reliable. His reliability and credibility, therefore, were adequately established. See: Commonwealth v. Carlisle, supra; Commonwealth v. White, supra.
The same cannot be said with respect to the evidence obtained through the use of the wiretap installed upon Jerry DiJoseph’s telephone. The affidavit in support of this wiretap application relied exclusively upon evidence obtained through the pen register which had been installed on Richard Mastro’s telephone. Without this evidence, the affidavit would have been insufficient to establish probable cause. Thus, were we not constrained to recognize a good faith exception to the exclusionary rule, the evidence obtained through this last wiretap would have to be deemed insufficient to show probable cause.
The orders suppressing evidence obtained by using pen registers and wiretaps as well as the physical evidence seized pursuant to search warrants are reversed. The case is remanded for further proceedings. Jurisdiction is not retained.
BECK, J., files a dissenting opinion.. A DNR is a type of pen register which attaches to a telephone line and records the numbers dialed on that particular telephone and monitors the date, time, and length of time the telephone receiver is off the hook. It does not, however, monitor the contents of any communication or record the origin of any incoming calls. See: 18 Pa.C.S. § 5702; Commonwealth v. Beauford, 327 Pa.Super. 253, 259, 475 A.2d 783, 786 (1984), appeal dismissed, 508 Pa. 319, 496 A.2d 1143 (1985). At the time that this DNR was installed, judicial authorization was not required for the installation of pen registers. However, Bell Telephone Company required law enforcement officials to present a court order before installing pen registers.
. DiJoseph was not a defendant in any of the cases that form the basis of this appeal.
. In United States v. Leon, supra, the police had obtained a facially valid search warrant from a magistrate based upon facts found by the magistrate to constitute probable cause. Some of the evidence seized pursuant to the warrant was later suppressed when the district court determined that the affidavit in support of the warrant application had been insufficient to establish probable cause. The Court of Appeals for the Ninth Circuit affirmed this determination. On further *440appeal, the Supreme Court of the United States reversed, holding that although the magistrate’s issuance of the warrant had been erroneous, "the officers’ reliance on the magistrate’s determination of probable cause [had been] objectively reasonable, and [therefore] the application of the extreme sanction of exclusion [was] inappropriate.” United States v. Leon, supra 468 U.S. at 926, 104 S.Ct. at 3423, 82 L.Ed.2d at 701. The facts in the instant case, although distinguishable from those in Leon, are even more compelling of the result we reach today.