“County peace officer” shall also include employees of the sheriff employed to attend sessions of the superior or former municipal courts and preserve order in the courtrooms, to guard and maintain the security of prisoners during court appearances, or to summon jurors and take responsibility for them while they are deliberating or absent from the courtroom. It shall not include persons employed as clerks, typists, teachers, instructors or psychologists.

This section shall not apply to any contracting agency nor to the

employees of a contracting agency until the agency elects to be subject to this section by amendment to its contract with the board, made as provided in Section 20474 or by express provision in its contract with the board.