Opinion by
Jacobs, J.,The issue presented in this appeal is the constitutionality of the Muncy Act, the state statute providing for sentencing of women to the State Correctional Institution at Muncy.
Appellant, Jane M. Daniels, was tried before the Hon. James L. Steen without a jury on charges of burglary, aggravated robbery, carrying a concealed deadly weapon, and possession of a firearm after conviction of a crime of violence. She was found guilty of robbery on May 3, 1966, and Judge Steen sentenced her that same day to a one to four year prison term in Philadelphia County Prison. On June 3, 1966, thirty-one days after the imposition of this sentence, Judge Steen vacated the original sentence and resentenced appellant to an indefinite term of imprisonment in the State Correctional Institution at Muncy. In accordance with the Muncy Act, the sentence was a general one fixing no maximum or minimum. From that sentence appellant appealed to this court, contending that her sentence to an indeterminate term at Muncy is improper since the applicable statute provides for an unconstitutional distinction between males and females as to sentencing.
The sentencing provisions of the act, herein referred to as the Muncy Act, provide as follows :
“Any court of record in this Commonwealth, exercising criminal jurisdiction, may, in its discretion, sentence to the State Industrial Home for Women (State Correctional Institution at Muncy) any female over sixteen years of age, upon conviction for, or upon pleading guilty of, the commission of any criminal offense punishable under the laws of this State. After due no*159tice given to all courts of record exercising criminal jurisdiction in this Commonwealth by the board of trustees of said State Industrial Home for Women that the said home is prepared to receive all women so com victed or pleading guilty of an offense punishable by imprisonment for more them a year who shall be sentenced to imprisonment, such sentence in all cases shall be to confinement in said State Industrial Home fór Women. Every sentence imposed pursuant to this act shall be merely a general one to the State Industrial Home for Women, and shall not fix or limit the duration thereof. The duration of such imprisonment, including the time spent on parole, shall not exceed three years, except where the maximum term specified by law for the crime for which the prisoner was sentenced shall exceed that period, in which event such maximum term, including the time spent on parole, shall be the limit of detention under the provisions of this act.” 1913, July 25, P. L. 1311, §15; 1925, May 14, P. L. 697, §1; 1931, June 22, P. L. 859, §1, 61 P.S. §566 (emphasis added).
I.
The first question that must be answered is whether Judge Steen had the power to vacate the original sentence and resentence appellant. Since the second sentence was imposed after the term at which appellant was convicted and more than 30 days after her conviction, Judge Steen was impowered to vacate the original sentence only if it was illegal. See Act of June 1, 1959, P. L. 342, §1, 12 P.S. §1032; Commonwealth ex rel. Perrotta v. Myers, 203 Pa. Superior Ct. 287, 201 A. 2d 292 (1964); Commonwealth ex rel. Firmstone v. Myers, 207 Pa. Superior Ct. 453, 217 A. 2d 851 (1966). The legality of the original sentence depends on whether the Muncy Act is the exclusive authority under *160which Jane Daniels could have been sentenced. Judge Stern concluded that he did have to sentence appellant under the Muncy Act and that his previous imposition of one to four year sentence in the Philadelphia-County prison was illegal. We agree with Judge Sterna’s conclusion that sentence to Muncy is mandatory where' a woman is convicted of a crime punishable by imprisonment for more than a year and some imprisonment is to be imposed.
In the original Muncy Act passed in 1913, sentence to Muncy was within the discretion of the court. Act of July 25, 1913, P. L. 1311, §15. The legislature in 1925 added the following language: “After due notice given to all courts of record exercising criminal jurisdiction in this Commonwealth by the board of trustees of said State Industrial Home for Women that the said home is prepared to receive all women so convicted or pleading guilty of an offense punishable by imprisonment for more than a year who shall be-sentenced to imprisonment, such, sentence in all cases shall he to confinement in said State Industrial Home for Women.” 1925, May 14, P. L. 697. (Emphasis added). The language of this amendment is simple and plain. No ambiguity whatsoever is present. Where the language of a statute is plain and unambiguous it must be given its obvious meaning. Davis v. Sulcowe, 416 Pa. 138, 205 A. 2d 89 (1964). It is clear’to us that the legislature intended to make sentence to Muncy the sole method of incarceration for any woman convietéd of a crime punishable by more than a year of imprisonment.
However, it is urged that the act of February 8, 1842, P. L. 12, §11, 19 P.S. §1022, authorizes the sentencing of women for more than one year to the Philadelphia County Prison. Whether this 1842 Act was impliedly repealed by the Muncy Act need nót be decided because the legislature specifically repealed it by *161the. Act of December .27, 1965, P. L. 1237, 61 P.S. §460.5. The latter act did not specifically repeal the Muncy Act nor did it by implication since it speaks only of sentences where a maximum is imposed and the Muncy Act. provides only for a general sentence to Muncy.
Appellant having, been convicted of a crime punishable by more than one year of imprisonment,1 the original sentence to the Philadelphia County Prison was illegal and Judge Stern acted properly in resentencing appellant.
II.
Appellant contends that the sentencing provisions of the Muncy Act, supra, are unconstitutional in that they deny her by reason of her sex the equal protection of law as required by the 14th Amendment to the United States Constitution.2
The Muncy Act does provide a different sentence for women .than for men convicted of the same crime. Where, a woman is sentenced to imprisonment the sentence is a general one to the institution at Muncy and the limits of the imprisonment are not fixed in the sentence.-
A male offender sentenced to imprisonment for robbery. is sentenced under the Act of June 19, 1911, P. L. 1055, §6, as amended, 19 P.S. §1057. That act calls for a sentence for an indefinite term, but directs the judge to.fix the minimum and maximum limits with the further proviso that the maximum may not exceed *162the maximum prescribed by law for such offense and the minimum shall never exceed one-half of the maximum prescribed by the judge.
In asking this court to declare a part of the Muncy Act unconstitutional, appellant has assumed a very heavy burden of proof. There is a strong presumption in favor of the constitutionality of acts of the legislature, e.g., New York v. O’Neill, 359 U.S. 1, 79 S. Ct. 564, 3 L. ed. 2d 585 (1959); Loomis v. Philadelphia School District Board, 376 Pa. 428, 103 A. 2d 769 (1954), and this court will not declare an act of the legislature to be unconstitutional unless it is shown to be “clearly, palpably and plainly” in violation of the constitution. Milk Control Commission v. Battista, 413 Pa. 652, 659, 198 A. 2d 840 (1964); Daly v. Hemphill, 411 Pa. 263, 271, 191 A. 2d 835, 840 (1963); Greenville Borough v. Guerrini, 208 Pa. Superior Ct. 42, 46, 220 A. 2d 366 (1966).
The legislature in enacting the Muncy Act has decided that women as a class are to be treated differently than men as to the term and manner of incarceration for crimes. The fact that legislation might impose greater burdens on one class of citizens does not in itself violate the Equal Protection Clause. As was said by the Supreme Court in Rinaldi v. Yeager, 384 U.S. 305, 86 S. Ct. 1497, 16 L. ed. 2d 577, 580 (1966), that clause “imposes a requirement of some rationality in the nature of the class singled out. To be sure, the constitutional demand is not a demand that a statute necessarily apply equally to all persons. ‘The Constitution does not require things which are different in fact ... to be treated in law as though they were the same. . / Hence, legislation may impose special burdens upon defined classes in order to achieve permissible ends.” In a recent case the Supreme Court of this state held that imposing the added burden of oral exams on women candidates for police sergeant did not *163violate the Equal Protection Clause. Wells v. Civil Service Commission, 423 Pa. 602, 225 A. 2d 554 (1967). A classification by the legislature would violate the Equal Protection Clause only if it did not rest upon a difference between the classes that bore a reasonable relation to the purposes of the legislation. E.g., McLaughlin v. Florida, 379 U.S. 184, 85 S. Ct. 283, 13 L. ed. 2d 222 (1964); Hoyt v. Florida, 368 U.S. 57, 82 S. Ct. 159, 7 L. ed. 2d 118 (1961); Milk Control Commission v. Battista, supra. The test stated by our Supreme Court is that a classification violates the Equal Protection Clause if it is shown to be patently arbitrary or utterly lacking in rational justification. Milk Control Commission v. Battista, supra. Of course, where fundamental rights and personal liberties may be affected by a classification, as they are here, the classification must be closely scrutinized and carefully confined. Harper v. Virginia State Board of Elections, 383 U.S. 663, 86 S. Ct. 1079, 16 L. ed. 2d 169, 174 (1966).3
Is there a rational basis for the classification, i.e., a reasonable connection between the classification by sex and the purposes of the legislation? The broad *164purpose of the legislation was to provide for the punishment and rehabilitation of prisoners. Different types of incarceration for the same crimes are regularly imposed both for classes of individuals (e.g., juveniles,4 sex offenders, recidivists, criminally insane), as well as among separate individuals where judicial discretion in imposing sentence may be allowed by the legislature. The only requirement for different treatment for different classes of persons is that the class exhibits characteristics that justify the different treatment. As was said by the Oregon Supreme Court in upholding a statute applying different treatment for sex offenders: “It is the province of the legislature to establish the penalties for the violation of the various criminal statutes and if the penalties are founded upon an arguably rational basis we have no authority to hold that they are invalid.” Jensen v. Gladden, 231 Ore. 141, 372 P. 2d 183, 185 (1962). This court is of the opinion that the legislature reasonably could have concluded that indeterminate sentences should be imposed on women as a class, allowing the time of incarceration to be matched to the necessary treatment in order to provide more effective rehabilitation. Such a conclusion could be based on the physiological and psychological make-up of women, the type of crime committed by women, their relation to the criminal world, their roles in society, their unique vocational skills and pursuits, and their reaction as a class to imprisonment, as well as the number and type of women who are sentenced to imprisonment rather than given suspended sentences. Such facts could have led the legislature to conclude that a different manner of *165punishment and rehabilitation was necessary for women sentenced to confinement.5
To support her attack on the legislation appellant argues that because she is a woman she has received a maximum sentence of ten years (the maximum for robbery); that if she were a man she would have received a maximum term of four years (the term imposed before the sentence was corrected to conform with the Muncy Act requirements); and that this difference in maximum terms solely because of her sex demonstrates a violation of the Equal Protection Clause of the 14th Amendment. This argument rests on an invalid assumption, viz., that a man committing this crime would have received a maximum term of four years. Judge SterNs prior sentence of one to four years was a sentence imposed upon Jane Daniels, a female, and we cannot speculate as to what the sentence would have been had the person robbing the bar in question been a male. She also argues that solely because she is a woman she will not become eligible for parole for at least three years and will not be discharged from the sentence for ten years. This argument is not legally accurate. The exclusive power of parole where the maximum sentence is two years or more is vested in the Pennsylvania Board of Probation and Parole by the Act of August 6, 1941, P. L. 861, as amended, 61 P.S. §§331.1-331.34. The board has such exclusive power over the inmates of Muncy where as *166here the maximum of the crime for which the inmate was sentenced is two years or more. 61 P.S. §331.31. Except in the case of prisoners condemned to death or serving life imprisonment the board has the power to parole any woman prisoner the day she enters Muncy6 but in the case of a male prisoner such power may not be exercised until the minimum term fixed by the court has expired. 61 P.S. §331.21. Appellant apparently assumes that a woman in Muncy cannot be discharged from her sentence until the maximum for the crime has expired but offers no authority to support this assumption. In fact, the Pennsylvania Board of Probation and Parole has been acting on the belief it has the power under the Muncy Act to terminate a woman’s sentence after three years, although it has no power to terminate a man’s sentence prior to the expiration of his maximum.
In effect, appellant presents us with arguments against the legislation without supporting data and asks us to reweigh the wisdom of the act of the legislature. This we cannot do. As the United States Supreme Court once said, “at most these arguments do no more than demonstrate that the question is debatable. And, if so, the effect of the action of the state legislature in passing the statute was to decide this debatable question against the view now advanced by appellant; and since we are unable to say that such a determination by the legislature is clearly unfounded, we are precluded from overturning it.” Bayside Fish Flour Co. v. Gentry, 297 U.S. 422, 430, 56 S. Ct. 513, 80 L. ed. 772, 778 (1936). Cf. Winston v. Moore, 244 Pa. 447, 91 A. 520 (1914).
We have examined the recent United States Supreme Court decisions concerning the Equal Protection Clause *167and find them to be harmonious with our decision in the present case. In Rinaldi v. Yeager, supra; Baxstrom v. Herold, 383 U.S. 107, 86 S. Ct. 760, 15 L. ed. 2d 620 (1966); Carrington v. Rash, 380 U.S. 89, 85 S. Ct. 775, 13 L. ed. 2d 675 (1965); and McLaughlin v. Florida, supra, in which various state laws were held invalid as in violation of the equal protection clause, the court found that the reasons given to support the classifications did not relate to the purposes of the legislation. On the contrary, in the present case there are differences between the sexes that the legislature could have concluded were related to the purposes of the legislation and these stand unrefuted by appellant. This situation is similar to that in Hoyt v. Florida, supra, in which the Supreme Court upheld different jury service laws for men and women as not in violation of the 14th Amendment.
Our research indicates that all the states that have considered statutes similar to the Muncy Act have upheld them as not in violation of the 14th Amendment. Ex parte Gosselin, 141 Me. 412, 44 A. 2d 882 (1945); Ex parte Brady, 116 Ohio St. 512, 157 N.E. 69 (1927); Platt v. Commonwealth, 256 Mass. 539, 152 N.E. 914 (1926); State v. Heitman, 181 P. 630 (Kans. 1919).
In short, appellant has not produced the facts necessary to refute the conclusion of the legislature that women require a different type and manner of incarceration. Were we to decide that the legislation in question was “patently arbitrary or utterly lacking in rational justification” in its application to women we would be putting allegations based on speculation ahead of the studied decision of the legislature with all of its fact-finding apparatus.
J udgment of sentence affirmed.
Under the Act of June 24, 1939, P. L. 872, §704, 18 P.S. §4704, the crime of robbery is punishable by a sentence not exceeding ten yéárs.
The Equal Protection Clause of the 14th Amendment provides: “No State shall . . . deny to any person within its jurisdiction the equal protection of the laws.”
In certain eases where a classification results in restricting personal liberties such as freedom of speech or which involve a racial classification, the classification is specially suspect and the state in the first instance must show a subordinating interest that is compelling. Griswold v. Connecticut, 381 U.S. 479, 85 S. Ct. 1678, 14 L. ed. 2d 510 (1965); McLaughlin v. Florida, supra; Shelton v. Tucker, 364 U.S. 479, 81 S. Ct. 247, 5 L. ed. 2d 231 (1960); Bates v. Little Rock, 361 U.S. 516, 80 S. Ct. 412, 4 L. ed. 2d 480 (1960). But in those cases, except ones involving racial discrimination, it is not the classification that is in question, but it is the necessity of the law itself that must be justified once it is shown that it invades the fundamental rights of certain groups. Unlike those cases, here there can be no question of the necessity of the punishment and rehabilitation of those convicted of crime, nor is there any question that a punitive statute is the type that does justifiably subordinate certain fundamental rights of those convicted.
See Commonwealth ex rel. Clawges v. Claudy, 173 Pa. Superior Ct. 410, 98 A. 2d 225 (1953), where this court held that the act providing for sentence of juvenile offenders to the Pennsylvania Industrial School at Camp Hill was not a denial of equal protection or due process.
A 1965 study of the Pennsylvania Board of Parole (Report on Women Parolees, March 31, 1965) records that over a ten year period (1947-1957) 16% of the women were returned to prison while the rate for men was 30%. Regardless of whether this is attributable to the different rehabilitation program for women or Whether it is attributable to some inherent difference between males and females in their relation to crime, it does demonstrate that there is some difference between men and women in regard to imprisonment and parole.
See Commonwealth eat rel. Clawges v. Claudy, supra, note 4, at p. 416.