N.J. Stat. § 43:9A-6
Any person who desires to take advantage of the benefits of this act shall file with the county treasurer, upon his appointment as clerk or deputy clerk of any district court of the judicial district which includes all of the territory within the boundaries of the county of the first class, an authorization, in writing, to such county treasurer for the deduction of three per centum (3%) of the amount of his salary during his continuance as clerk or deputy clerk of such district court, and thereafter there shall be deducted from every payment of salary to such person three per centum (3%) of the amount thereof, so long as he shall remain in such public office or position or until his retirement under this act, for the use of the county.
N.J.S. § 43:9A-6