N.J. Stat. § 40:47-12
Whenever a former policeman or fireman is reappointed pursuant to section 1 of this act and the membership of such person in the pension system created pursuant to P.L. 1944, chapter 255, or the pension system created pursuant to P.L. 1954, chapter 84, has been terminated and contributions of such member returned to him, he shall be reinstated in the pension system upon reappointment pursuant to this act and upon his repurchase of credit for all of his previous membership service in such pension system. Such repurchase shall be effected by his paying into the annuity savings fund of the pension the amount required by applying the factor, supplied by the actuary, as being applicable to his age at the time of the purchase, to his salary at that time.
N.J.S. § 40:47-12