I have gotten several calls with this number in the Caller ID, but haven't, until now, posted anything.
My usual MO (Modus Operandi) is to wait 3 rings, pick up the handset, say nothing, listen for the caller to announce themselves. Usually the caller says nothing.
The short length calls are the ones I picked up, the long length calls are the ones I did not pick up, and the caller did not leave a message on my voice mail.
I know only one person in California, and he's retired, and does not work for a security company.

Name             Number              When                    Length

SECURITY     650-276-7132     Mon, 01-11-16     0:11
SECURITY     650-276-7132     Mon, 01-11-16     0:32
SECURITY     650-276-7132     Tue,  01-12-16     0:32
SECURITY     650-276-7132     Tue,  01-12-16     0:18
SECURITY     650-276-7132     Thu,  01-14-16     0:12
SECURITY     650-276-7132     Thu,  01-14-16     0:29
SECURITY     650-276-7132     Fri,    01-15-16     0:04
SECURITY     650-276-7132     Sat,   01-16-16     0:11
SECURITY     650-276-7132     Sat,   01-16-16     0:27