Cal. Gov. Code § 25103
The records and minutes of the board, acting in any capacity, shall be signed by the chairperson and the clerk. The board may by resolution authorize the use of a facsimile signature of the chairperson of the board acting in any capacity, where the board sits as the governing body, agency, or entity on all papers, documents, or instruments requiring the signature of the chairperson of the board, including all resolutions, orders, ordinances, contracts, minutes, notices, deeds, leases, papers and records of the board except that the original copy thereof, or the copy thereof filed in the office of the clerk of the board, shall bear the personal signature of the chairperson or shall have been delivered to him or her, and those papers, documents, or instruments bearing the facsimile signature shall be accorded the same force and effect as though personally signed by the chairperson. A certificate by the clerk that a copy of that document has been delivered to the chairperson of the board shall be prima facie evidence of the delivery.
If, in order to be recorded by the county recorder, the paper, document, or instrument requires the acknowledgement or verification of the person by whom it is executed, then it shall be recordable when the clerk acknowledges his or her signature upon the certificate which indicates that a copy of the paper, document, or instrument has been delivered to the chairperson.
In the case of a public security or any instrument of payment, the provisions of the Uniform Facsimile Signature of Public Officials Act (Chapter 6 (commencing with Section 5500) of Division 6 of Title 1 of the Government Code) shall govern.
If the facsimile signature of the chairperson of the board of supervisors is affixed to any document prior to November 23, 1970, the document shall have the same force and effect from the time of affixing as if the facsimile signature had been affixed after that date.
Ca. Gov. Code § 25103