Penal Code PC § 632
(b) For the purposes of this section, “person” means an individual, business association, partnership, corporation, limited liability company, or other legal entity, and an individual acting or purporting to act for or on behalf of any government or subdivision thereof, whether federal, state, or local, but excludes an individual known by all parties to a confidential communication to be overhearing or recording the communication.
(c) For the purposes of this section, “confidential communication” means any communication carried on in circumstances as may reasonably indicate that any party to the communication desires it to be confined to the parties thereto, but excludes a communication made in a public gathering or in any legislative, judicial, executive, or administrative proceeding open to the public, or in any other circumstance in which the parties to the communication may reasonably expect that the communication may be overheard or recorded.
(d) Except as proof in an action or prosecution for violation of this section, evidence obtained as a result of eavesdropping upon or recording a confidential communication in violation of this section is not admissible in any judicial, administrative, legislative, or other proceeding.
(e) This section does not apply (1) to any public utility engaged in the business of providing communications services and facilities, or to the officers, employees, or agents thereof, if the acts otherwise prohibited by this section are for the purpose of construction, maintenance, conduct, or operation of the services and facilities of the public utility, (2) to the use of any instrument, equipment, facility, or service furnished and used pursuant to the tariffs of a public utility, or (3) to any telephonic communication system used for communication exclusively within a state, county, city and county, or city correctional facility.
(f) This section does not apply to the use of hearing aids and similar devices, by persons afflicted with impaired hearing, for the purpose of overcoming the impairment to permit the hearing of sounds ordinarily audible to the human ear.