(a) The Illinois Department, or any officer or employee thereof designated in writing by the Illinois Department, shall at its or his own instance, or on the written request of any other party to the proceeding, issue subpoenas requiring the attendance of and the giving of testimony by witnesses, and subpoenas duces tecum requiring the production of books, papers, records or memoranda. The subpoenas and subpoenas duces tecum may be served by any person of full age. Any subpoena may be served in the same manner as a subpoena issued out of a circuit court, and may also be served by United States registered or certified mail, addressed to the person concerned at his last known address, and proof of such mailing shall be sufficient for the purposes of the Article.
     (b) Subpoenas duces tecum issued in other states shall be afforded full faith and credit in this State. Every such subpoena shall have the full force, effect, and attributes of a subpoena issued in this State, including the ability to be enforced.