(a) Subpoenas may be enforced by attachment for contempt and by a fine not exceeding $300.00 and imprisonment not exceeding 20 days. In all cases under this Code section, the court shall consider whether under the circumstances of each case the subpoena was served within a reasonable time, but in any event not less than 24 hours prior to the time that appearance thereunder was required.

(b) The court may also in appropriate cases grant continuance of the cause. Where subpoenas were issued in blank, no continuance shall be granted because of failure to respond thereto when the party obtaining them fails to present to the clerk the name and address of the witness so subpoenaed at least six hours before appearance is required.

(c) When books, papers, or documents are unsuccessfully sought, secondary evidence thereof shall be admissible.