California Code, Government Code - GOV § 8641

(a) To inform himself or herself of the duties of the office for which the officer stands by.  Officers and employees of the political subdivision shall assist the standby officer and each political subdivision shall provide each standby officer with a copy of this article.

(b) To keep informed of the business and affairs of the political subdivision to the extent necessary to enable the standby officer to fill his or her post competently.  For this purpose the political subdivision may arrange information meetings and require attendance.

(c) To immediately report himself or herself ready for duty in the event of a state of war emergency or in the event of a state of emergency or a local emergency at the place and in the method previously designated by the political subdivision.

(d) To fill the post for which he or she has been appointed when the regular officer is unavailable during a state of war emergency, a state of emergency or a local emergency.  Standby officers Nos. 2 and 3 shall substitute in succession for standby officer No. 1 in the same way that standby officer No. 1 is substituted in place of the regular officer.  The standby officer shall serve until the regular officer becomes available or until the election or appointment of a new regular officer.