QUINN, Justice.
We granted certiorari to review an order of the Boulder District Court affirming the ruling of the Boulder County Court which suppressed evidence obtained by the use of a pen register. The district court reasoned that under Article II, Section 7 of the Colorado Constitution a telephone subscriber has a legitimate expectation that information relating to telephone numbers dialed on a home telephone will remain private and that in the. absence of exigent circumstances law enforcement officers must obtain a search warrant supported by probable cause prior to the installation of a pen register. We affirm the order of the district court.
I.
The defendant, Diane Ruth Sporleder, was charged in the Boulder County Court with several misdemeanor counts of harassment by telephone, section 18-9-lll(l)(f), C.R.S.1973 (1978 Repl.Vol. 8).1 The defendant filed a motion to suppress the records of [137]*137all telephone numbers dialed by her which were obtained by the installation of a pen register. A hearing was held on the defendant’s motion to suppress and the following facts were established.
In October of 1979 Mountain Bell Telephone Company (Mountain Bell) received several complaints alleging that the defendant had made a series of harassing telephone calls. Robert Sprouse, Mountain Bell’s Security Manager, called the defendant and advised her of the complaints, but she denied being the source of the calls. The record does not indicate that Sprouse took any further action at that time.
Later, in February of 1980, the Boulder District Attorney’s Office received a complaint in the form of a sworn affidavit from Robert L. Finch, an attorney in Farming-ton, New Mexico. Finch stated that he and his law partner had received a series of anonymous, annoying telephone calls at their office and homes. According to the affidavit, once the telephone was answered the caller would hang up immediately. Finch’s affidavit continued:
“By coincidence I have discovered that a client of mine, Mr. Dudley Pounders, had endured these types of calls for months. The source of the telephone calls has been identified by Mountain Bell employees as coming from the residence of Diane Ruth Spoleder [sic], 1604 Sunset, Louisville, Colorado. This office represented Mr. Pounders in a particularly acrimonious divorce action with Ms. Spoleder [sic] and is currently handling another matter between the parties. Additionally, other attorneys in this locale who formerly represented Ms. Spoleder [sic] are receiving similar calls. The pattern with all calls to all individuals is identical.”
In the meanwhile Mountain Bell continued to receive complaints of abusive telephone calls. Security Manager Sprouse contacted James Smith, Chief Investigator for the Boulder District Attorney’s Office, and was assured that the district attorney’s office was “handling the ease” and would keep Sprouse advised. On April 24, 1980, Sprouse again called Smith to determine the status of the investigation. Smith at this time initially requested Sprouse to disconnect the defendant’s telephone, but later they both decided to conduct a joint “deterrent interview” with her and they accordingly telephoned her at home on that date. When she answered the telephone, Sprouse identified himself and warned her that if the calls continued her telephone service would be disconnected. The defendant denied making any harassing telephone calls, at which point Smith revealed his presence on the line and warned her that criminal charges could be filed. The following day Mountain Bell sent the defendant a followup letter advising her that it knew of her harassing telephone calls, that “Mr. Jim Smith of the Boulder District Attorney’s Office is also aware of this situation,” and that “if we are notified that you have made one more call to harass or threaten any of the [complainants] your telephone service will be terminated immediately.”
On May 8, 1980, a pen register was installed on the defendant’s home telephone. A pen register is a mechanical device that records the numbers dialed on a telephone by monitoring the electrical impulses caused when the dial on the telephone is released, without, however, recording or monitoring the telephone conversation.2 The pen register was installed at the office of Mountain Bell and recorded the date, time and telephone number of the calls from the defendant’s telephone. The tape of the pen register indicated that between May 9 and May 16 several telephone numbers listed to the persons who had previously complained of harassing calls were dialed from the defendant’s telephone.
At the close of the evidentiary hearing on the motion to suppress the county court continued the matter for briefs and legal argument. The People filed a brief chal[138]*138lenging the defendant’s suppression motion on the single ground that the defendant had no legitimate expectation of privacy in the telephone numbers dialed by her on her telephone. During the subsequent legal argument before the county court, the court expressly inquired of the deputy district attorney whether the prosecution was contending that there was a lack of any governmental action in this case. The deputy district attorney responded that the prosecution’s basic contention was that a telephone user had no legitimate expectation of privacy in telephone numbers dialed by her. The county court granted the motion to suppress the evidence obtained from the use of the pen register, ruling that in the absence of exigent circumstances, Article II, Section 7 of the Colorado Constitution requires law enforcement officials to obtain a search warrant in order to install a pen register on a suspect’s telephone.
The People appealed this ruling to the Boulder District Court, arguing that because the defendant had no legitimate expectation of privacy in the telephone numbers dialed by her, the installation of the pen register implicated no right under the Colorado Constitution. The district court, also noting that “[t]he presence of governmental action is not contested,” affirmed the suppression ruling of the county court and concluded, in pertinent part, as follows:
“Although the state has a legitimate interest in maintaining public order, the telephone subscriber has a legitimate privacy interest in the records of telephone calls made from [her] own home. Before the state is permitted to search or create these records by means of a pen register, a search warrant must be issued upon a showing of probable cause. The pen register search of defendant Sporleder’s telephone was conducted without a warrant and is therefore violative of Article II, Section 7 of the Colorado Constitution. Accordingly, the suppression of the pen register tapes is affirmed.”
The People’s principal argument before this court is that the defendant had no legitimate expectation of privacy in the telephone numbers she dialed and, hence, the use of the pen register to obtain that information was not an unconstitutional search and seizure in violation of Article II, Section 7 of the Colorado Constitution. Alternatively, the People argue that even if the defendant’s privacy expectation was a legitimate one, the installation of a pen register should be authorized on a standard less than the probable cause required for a search warrant. Before considering these arguments, it is necessary that we address the threshold matter of state action.
II.
The People contend that there was no state action in the installation of the pen register and, therefore, no violation of the defendant’s constitutional rights. Although the record suggests an ongoing joint investigation by the district attorney’s office and Mountain Bell during the period when the pen register was installed on the defendant’s telephone line, we need not determine here whether the interactions between the district attorney’s office and Mountain Bell were sufficient to render the telephone company a “state agent” for purposes of the constitutional protection against unreasonable searches and seizures.3 See Lustig [139]*139v. United States, 338 U.S. 74, 69 S.Ct. 1372, 93 L.Ed. 1819 (1949) (as long as federal agent was in some way involved before the object of the search was accomplished, it is immaterial whether he initiated or joined in the search); Corngold v. United States, 367 F.2d 1 (9th Cir.1966) (search of airline shipment which was joint operation of federal and airline agents deemed state action). The reason we need not decide the issue in this case is because the prosecution during the proceedings below did not oppose the defendant’s suppression motion on the basis of any lack of state action in regard to the installation of the pen register. Rather, the prosecution’s basic contention throughout the suppression hearing as well as in the district court appeal was that the defendant, as a telephone subscriber, had no legitimate expectation of privacy in the telephone numbers dialed by her. Indeed, the district court expressly noted the prosecution’s concession of state action in its written order affirming the county court’s suppression ruling, and the prosecution never raised the issue of state action in its petition for certiorari. Under the circumstances of this case, therefore, the People have clearly abandoned any claim relating to the asserted lack of state action in the installation of the pen register on the defendant’s telephone line.4 See Steagald v. United States, 451 U.S. 204, 101 S.Ct. 1642, 68 L.Ed.2d 38 (1981) (government loses its right to raise a defendant’s lack of standing to challenge a search when it acquiesces in contrary findings or fails to raise the issue in a timely fashion during litigation); People v. Hearty, 644 P.2d 302 (Colo.1982) (where district attorney at a suppression hearing initially objected to defendant’s standing to contest search of an attorney’s office, but later withdrew any objection on that basis, prosecutorial contention on appeal that defendants lacked standing was deemed waived). We therefore turn to the other issues raised by the People.
III.
The People’s principal argument is that the defendant had no legitimate expectation of privacy in the telephone numbers she dialed on her home telephone and, hence, the warrantless installation of the pen register did not violate the Colorado constitutional prohibition against unlawful searches and seizures. We disagree.
Article II, Section 7 of the Colorado Constitution provides:
“The people shall be secure in their persons, papers, houses and effects, from unreasonable searches and seizures; and no warrant to search any place or seize any person or things shall issue without describing the place to be searched, or the person or thing to be seized, as near as may be, nor without probable cause, supported by oath or affirmation reduced to writing.”
As in the case of the Fourth Amendment to the United States Constitution, see Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967), the purpose of the Colorado constitutional provision is to protect a person’s legitimate expectation of privacy from unreasonable governmental intrusions. E.g., Charnes v. DiGiacomo, 200 Colo. 94, 612 P.2d 1117 (1980); People v. Bement, 193 Colo. 435, 567 P.2d 382 (1977); People v. Counterman, 192 Colo. 152, 556 P.2d 481 (1976); People v. Weisenberger, 183 Colo. 353, 516 P.2d 1128 (1973). In determining [140]*140the legitimacy of the defendant’s privacy expectation the appropriate inquiry is whether she expected that the numbers dialed by her on her home telephone would be free from governmental intrusion, and, if she did, whether that expectation is one that society is prepared to recognize as reasonable. See, e.g., People v. Gomez, 632 P.2d 586 (Colo.1981), cert. denied, 455 U.S. 943, 102 S.Ct. 1439, 71 L.Ed.2d 655 (1982); Charnes v. DiGiacomo, supra; People v. Weisenberger, supra. In our opinion the defendant’s privacy expectation, when measured against this dual standard, qualifies for constitutional protection under Article II, Section 7 of the Colorado Constitution.
A.
In Smith v. Maryland, 442 U.S. 735, 99 S.Ct. 2577, 61 L.Ed.2d 220 (1979), the United States Supreme Court considered “whether the installation and use of a pen register constitutes a ‘search’ within the meaning of the Fourth Amendment.” Id. at 736, 99 S.Ct. at 2578, 61 L.Ed.2d at 224. The majority reasoned that “telephone users realize that they must ‘convey’ phone numbers to the telephone company,” id. at 742, 99 S.Ct. at 2581, 61 L.Ed.2d at 228, and that any subjective expectation of privacy in telephone numbers dialed is not “one that society is prepared to recognize as ‘reasonable.’ ” Id. at 743, 99 S.Ct. at 2582, 61 L.Ed.2d at 229. Since, in the Court’s view, “a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties,” no Fourth Amendment violation occurred in the installation and use of the pen register. Id. at 743-44, 99 S.Ct. at 2582, 61 L.Ed.2d at 229.
Although Article II, Section 7 of the Colorado Constitution is substantially similar to its federal counterpart, we are not bound by the United States Supreme Court’s interpretation of the Fourth Amendment when determining the scope of state constitutional protections. E.g., Charnes v. DiGiacomo, supra; Denver v. Nielson, 194 Colo. 407, 572 P.2d 484 (1977); People v. Hoinville, 191 Colo. 357, 553 P.2d 777 (1976). See also Brennan, State Constitutions and the Protection of Individual Rights, 90 Harv.L.Rev. 489 (1977); Note, The New Federalism: Toward a Principled Interpretation of the State Constitution, 29 Stan.L.Rev. 297 (1977). In DiGiaeomo, for example, we rejected the United States Supreme Court’s holding in United States v. Miller, 425 U.S. 435, 96 S.Ct. 1619, 48 L.Ed.2d 71 (1976), that a bank depositor has no reasonable expectation of privacy in checks and deposit slips voluntarily conveyed to the bank and exposed to bank employees in the ordinary course of business. The disclosure to banks of information about the depositor’s financial transactions, in our opinion, was a mere by-product of the depositor’s major purpose of utilizing the bank as a vehicle for fund transfers and was not a true disclosure to a third person such as would vitiate the depositor’s reasonable expectation of privacy in bank records relating to his financial transactions. The depositor’s privacy expectation led us to conclude that he had standing “to raise the legitimacy of governmental access to the records in a motion to quash the subpoena for the records.” Supra 612 P.2d at 1122.5 [141]*141We believe the rationale of DiGiacomo applies in a comparable manner to the pen register record of telephone calls dialed by the defendant in this case.
B.
A telephone subscriber such as the defendant has an actual expectation that the dialing of telephone numbers from a home telephone will be free from governmental intrusion. A telephone is a necessary component of modern life. It is a personal and business necessity indispensable to one’s ability to effectively communicate in today’s complex society. When a telephone call is made, it is as if two people are having a conversation in the privacy of the home or office, locations entitled to protection under Article II, Section 7 of the Colorado Constitution. The concomitant disclosure to the telephone company, for internal business purposes, of the numbers dialed by the telephone subscriber does not alter the caller’s expectation of privacy and transpose it into an assumed risk of disclosure to the government. “Privacy is not a discrete commodity, possessed absolutely or not at all. Those who disclose certain facts to a ... phone company for a limited business purpose need not assume that this information will be released to other persons for other purposes.” Smith v. Maryland, supra 442 U.S. at 749, 99 S.Ct. at 2585, 61 L.Ed.2d at 232 (Marshall, J., dissenting). Besides, it is somewhat idle to speak of assuming risks in a context where, as a practical matter, the telephone subscriber has no realistic alternative. Id. at 749-50, 99 S.Ct. at 2585, 61 L.Ed.2d at 232-33 (Marshall, J., dissenting).
We view the disclosure to the telephone company of the number dialed as simply the unavoidable consequence of the subscriber’s use of the telephone as a means of communication and the telephone company’s method of determining the cost of the service utilized. Indeed, telephone companies have not been insensitive to the confidentiality of this information. See Reporters Committee For Freedom of the Press v. American Telephone & Telegraph, 593 F.2d 1030, 1038 (D.C.Cir.1978), cert. denied, 440 U.S. 949, 99 S.Ct. 1431, 59 L.Ed.2d 639 (1979) (noting A.T. & T. policy which prohibits the release of toll billing records in the absence of a valid subpoena, its policy requiring notification to telephone subscribers of the subpoena in civil suits and noncriminal investigations, and also its policy requiring similar notification to subscribers in felony investigations unless the subpoena certifies that such notice could impede the investigation). See also Claerhout, The Pen Register, 20 Drake L.Rev. 108, 115-16 (1970). A person’s privacy expectation should not depend on “risks an individual can be presumed to accept when imparting information to third parties, but on the risks he should be forced to assume in a free and open society.” Smith v. Maryland, supra 442 U.S. at 750, 99 S.Ct. at 2585, 61 L.Ed.2d at 233 (Marshall, J., dissenting). Any use the telephone company might make of such information for its own internal accounting purposes is far different from governmental evidence gathering. See Note, Pen Registers After Smith v. Maryland, 15 Harv.C.R. — C.L.L. Rev. 753, 765-66 (1980). We have no doubt, therefore, that the defendant expected that the telephone numbers which she dialed from her telephone would remain free from governmental intrusion.
We are also convinced that the defendant’s expectation that the numbers dialed on her telephone would remain free from governmental intrusion is a reasonable one. The mere fact that “our ordinary social intercourse, uncontrolled by government, imposes certain risks upon us hardly means that government is constitutionally unconstrained in adding to those risks.” Amsterdam, Perspectives on the Fourth Amendment, 58 Minn.L.Rev. 349, 406 (1974). The pen register recorded each telephone number dialed by the defendant as well as the [142]*142date and time of each telephone call. Knowledge of these facts can often yield inferential knowledge of the content of the conversation itself. In addition, a pen register record holds out the prospect of an even greater intrusion in privacy when the record itself is acquired by the government, which has a technological capacity to convert basic data into a virtual mosaic of a person’s life.
One’s disclosure of certain facts to the telephone company as a necessary concomitant for using an instrument of private communication hardly supports the assumption that the company will voluntarily convey that information to others. Telephone companies are in the business of providing telephone subscribers with the equipment necessary for electronic communication in today’s world. The government, in contrast, investigates for the purpose of prosecuting persons for criminal offenses. The expectation that information acquired by the telephone company will not be transferred without legal process, to the government for use against the telephone subscriber appears to us to be an eminently reasonable one.
We agree in this respect with the reasoning of the New Jersey Supreme Court in State v. Hunt, 91 N.J. 338, 450 A.2d 952 (1982). There the court held that the New Jersey Constitution granted a telephone subscriber a constitutionally protected privacy interest in the telephone company’s home toll billing records for the subscriber’s telephone. After noting that the expectation of privacy in toll billing records, which reflect long distance completed calls, is substantially similar to the privacy interest in the pen register, which identifies all local and long distance calls, the court observed:
“It is unrealistic to say that the cloak of privacy has been shed because the telephone company and some of its employees are aware of this information. Telephone calls cannot be made except through the telephone company’s property and without payment to it for the service. This disclosure has been necessitated because of the nature of the instrumentality, but more significantly the disclosure has been made for a limited business purpose and not for release to other persons for other reasons. The toll billing record is a part of the privacy package.” Id. at 347, 450 A.2d at 956.
See also People v. Blair, 25 Cal.3d 640, 602 P.2d 738, 159 Cal.Rptr. 818 (1979) (“[a]s in the case of a telephone call from a private residence, a hotel guest may reasonably expect that the calls which he makes from his room are recorded by the hotel for billing purposes only, and that the record of his calls will not be transmitted to others without legal process”); People v. McKunes, 51 Cal.App.3d 487, 124 Cal.Rptr. 126 (1975) (legitimate expectation that record of numbers called will be used only for telephone company’s internal accounting purposes). Simply stated, merely because the telephone subscriber has surrendered some degree of privacy for a limited purpose to those with whom she is doing business does not render the subscriber “fair game for unrestrained police scrutiny” by virtue of that fact. 1 W. LaFave, Search and Seizure: A Treatise on the Fourth Amendment § 2.7 at 408 (1978). The defendant’s expectation of privacy in the numbers dialed on her home telephone is an expectation that we are prepared to recognize as reasonable under Article II, Section 7 of the Colorado Constitution.6
[143]*143c.
The People urge that our holding in Charnes v. DiGiacomo, supra, is not applicable here because that case dealt with the content of bank records while pen registers cannot record the content of telephone conversations. As noted above, a record indicating the various numbers, dates and times a telephone subscriber has communicated with another can furnish substantial information about the caller even when the content of those communications is not revealed. That pen registers do not result in actual monitoring of telephone conversations does not render the numbers themselves devoid of a significant privacy interest on the part of the caller. See District Attorney v. New England Telephone and Telegraph Co., 379 Mass. 586, 399 N.E.2d 866 (1980) (where state statute governing the interception of the “contents” of any wire or oral communication defined “contents” to include “any information concerning the identity of the parties to such communication or the existence ... of that communication,” the recording of incoming local call numbers by means of a cross frame unit trap falls within the scope of the statute because a telephone number is information “concerning the identity of a party” and “the existence of a communication”). Contrary to the People’s argument, any difference between a bank customer’s privacy interest in bank records and a telephone subscriber’s privacy interest in a record of telephone numbers dialed from a home telephone is too insubstantial to justify a constitutional differentiation in treatment.7
IY.
The People alternatively argue that even if constitutional protection extends to the use of pen registers, a standard short of probable cause should suffice to authorize their installation at the behest of the government. We disagree.
Article II, Section 7 of the Colorado Constitution interposes itself between the people and the government by generally requiring the procurance of a search warrant based on probable cause before the government can intrude into one’s legitimate privacy interests. See, e.g., McCall v. People, 623 P.2d 397 (Colo.1981); People v. Lorio, 190 Colo. 373, 546 P.2d 1254 (1976). While admittedly some forms of governmental intrusion are so narrow in scope and purpose and justified by such substantial law enforcement interests that they may be made on less than probable cause, see Michigan v. Summers, 452 U.S. 692, 101 S.Ct. 2587, 69 L.Ed.2d 340 (1981); Terry v. Ohio, 392 U.S. 1, 88 S.Ct. 1868, 20 L.Ed.2d 889 (1968); People v. Lewis, 659 P.2d 676 (Colo.1983), we are not dealing with such a limited intrusion in this case. Because a telephone subscriber has a legitimate expectation of privacy in the telephone numbers dialed, the installation of a pen register and the acquisition of information about the telephone numbers dialed by the subscriber is nothing less than a full-scale search and [144]*144seizure in the constitutional sense of those terms. The pen register “looks for” or “searches out” that which is otherwise concealed from governmental viewing. See W. LaFave, supra, § 2.1 at 222 (1978). Similarly, the creation and subsequent acquisition of the record of the telephone calls made is a “taking” or “seizing” of that information. Id.
In the absence of some narrowly defined exception to the warrant requirement, such as exigent circumstances or consent, neither of which is present in this case, a warrantless search is presumed to be invalid. E.g., People v. Hogan, 649 P.2d 326 (Colo.1982); People v. Casias, 193 Colo. 66, 563 P.2d 926 (1977); People v. Williams, 192 Colo. 249, 557 P.2d 399 (1976). Were we to permit an exception to the warrant requirement that would encompass the type of pervasive intrusion that occurred here, we would indeed permit the exception to become the norm, in derogation of the purpose of the warrant requirement itself. In the absence of exigent circumstances or consent, therefore, we decline to permit the governmental installation of a pen register without the procurement of a search warrant supported by probable cause.
V.
In summary, we hold that Article II, Section 7 of the Colorado Constitution provides a telephone subscriber with a legitimate expectation of privacy in the records of telephone numbers dialed, that such material is protected from unreasonable searches and seizures, that the installation of a pen register to record the numbers dialed constitutes a search, that the acquisition by means of the pen register of the record of the numbers dialed constitutes a seizure, and that in the absence of exigent circumstances or consent law enforcement officers may not procure the installation of a pen register without first obtaining a search warrant supported by probable cause.
The order of the district court is affirmed.
ERICKSON, C.J., and ROVIRA, J., dissent.