| A - Automated Security Gates | A - Automated Security Gates | — | (818) 720 4088 | Alarm and generators | Agua Dulce · Los Angeles County | — | — |
| A D Security INC | Adam David Stelzer | — | (626) 255 1562 | Alarm and generators | Sierra Madre · Los Angeles County | — | — |
| A P Alarm INC | Paval Adrian | — | (916) 791 4141 | Alarm and generators | Roseville · Placer County | — | — |
| A P S Overhead Door & Security Co | Randall Henry Scheppmann | — | (619) 588 6385 | Alarm and generators | El Cajon · San Diego County | — | — |
| A T D Lock & Security INC | Orly Zevulun | — | (818) 883 7199 | Alarm and generators | Tarzana · Los Angeles County | — | — |
| A To Z Car Stereo | A To Z Car Stereo | — | (951) 977-4442 | Alarm and generators | Murrieta · Alpine County | — | — |
| A V Knight Low Voltage Security | Oswaldo Antonio Barrera Rivera | — | (661) 202 9579 | Alarm and generators | Palmdale · Los Angeles County | — | — |
| A&s Low Voltage Security Services | Anthony Salgado Jr Urias | — | (661) 437 0807 | Alarm and generators | Bakersfield · Kern County | — | — |
| A-a Lock & Alarm INC | James Bruce Mac Lachlan | — | (650) 326 9020 | Alarm and generators | Menlo Park · San Mateo County | — | — |
| A-pro Security Services INC | Gregory Kipnis | — | (949) 635 0300 | Alarm and generators | Trabuco Canyon · Orange County | — | — |
| A1 Audio | A1 Audio | — | (559) 656-7999 | Alarm and generators | Tulare · Tulare County | — | — |
| Aaa Security Iron | Aaa Security Iron | — | (323) 497 3863 | Alarm and generators | North Hollywood · Los Angeles County | — | — |
| Absolute Lock And Security INC | Jeremiah Daniel Burdette | — | (818) 404 2112 | Alarm and generators | Newhall · Los Angeles County | — | — |
| Acc Security & Surveillance Camera Systems | Acc Security & Surveillance Camera Systems | service@securitycameralosangeles.com | (310) 966-9919 | Alarm and generators | Los Angeles · Los Angeles County | — | — |
| Access Lock & Security | Mark Guadalupe Hernandez | impallari@gmail.com | (661) 556 2849 | Alarm and generators | Bakersfield · Kern County | — | — |
| Access Security Solutions LLC | Babajide Kofi Williams | — | (510) 356 0083 | Alarm and generators | El Sobrante · Contra Costa County | — | — |
| Accurate Security Center | Accurate Security Center | — | (562) 869 2555 | Alarm and generators | Downey · Los Angeles County | — | — |
| Accurate Security Pros INC | Gregory Alan Parks | — | (858) 271 1155 | Alarm and generators | San Diego · San Diego County | — | — |
| Accuview Video Security INC | Brandon Michael Fackler | — | (661) 450 2288 | Alarm and generators | Palmdale · Los Angeles County | — | — |
| Ace Alarm INC | James Eung-Kyu Chang | — | (213) 739 0366 | Alarm and generators | Los Angeles · Los Angeles County | — | — |
| Acme Security Center INC | Jason David Herrington | — | (707) 546 2514 | Alarm and generators | Santa Rosa · Sonoma County | — | — |
| Acme Valley Security Services INC | Brett David Salles | — | (877) 266 6411 | Alarm and generators | Van Nuys · Los Angeles County | — | — |
| Acs Security | Acs Security | — | (310) 475-9016 | Alarm and generators | Los Angeles · Los Angeles County | — | — |
| Adi Global Distribution - Santa Clara | Adi Global Distribution - Santa Clara | becomeacustomer@adiglobal.com | (877) 228-6739 | Alarm and generators | Santa Clara · Santa Clara County | — | — |
| Adt Security Services | Adt Security Services | — | (858) 380-5542 | Alarm and generators | San Diego · San Diego County | — | — |
| Adt Security Services | Adt Security Services | — | (800) 743-4888 | Alarm and generators | Ventura · Ventura County | — | — |
| Adt Security Services | Adt Security Services | — | (805) 617-4719 | Alarm and generators | Goleta · Santa Barbara County | — | — |
| Adt Security Services | Adt Security Services | — | (559) 412-5906 | Alarm and generators | Fresno · Fresno County | — | — |
| Adt Security Services | Adt Security Services | — | (650) 458-0123 | Alarm and generators | Brisbane · San Francisco County | — | — |
| Adt Security Services 1934 And | Adt Security Services 1934 And | — | (916) 993-3522 | Alarm and generators | Sacramento · Sacramento County | — | — |
| Advance Services Inc. | Advance Services Inc. | — | (530) 379-0230 | Alarm and generators | Colusa · Colusa County | — | — |
| Advanced Security Systems | Advanced Security Systems | — | (707) 464-1975 | Alarm and generators | Crescent City · Mendocino County | — | — |
| Agile Security Group INC | Raymond Alexander Walton | — | (858) 877 9330 | Alarm and generators | Poway · San Diego County | — | — |
| Aj Alarm Systems | Aj Alarm Systems | al@ajalarmsystems.com | — | Alarm and generators | Orange · Orange County | — | — |
| Aji Low Voltage Security | Aji Low Voltage Security | — | (818) 826 8546 | Alarm and generators | San Fernando · Los Angeles County | — | — |
| Al & Ed's Autosound | Al & Ed's Autosound | — | (760) 758-9494 | Alarm and generators | Vista · Alpine County | — | — |
| Al & Ed's Autosound La Mesa | Al & Ed's Autosound La Mesa | — | (619) 343-3501 | Alarm and generators | La Mesa · Alpine County | — | — |
| Alan Ackerman DBA Altech Security Co | Alan Edward Ackerman | — | (818) 240 0729 | Alarm and generators | Glendale · Los Angeles County | — | — |
| Alarm C C T V Edge | Gary Lynn Lawhon | — | (925) 639 6111 | Alarm and generators | Concord · Contra Costa County | — | — |
| Alarm Fire Protection INC | Carol Anna Carri | — | (714) 998 1101 | Alarm and generators | Orange · Orange County | — | — |