They have called me twice, the first time was around 10pm, the second time was 4:11am.
There is no response from the caller, and no background noise, so I think it may be an auto dialer looking for a pulse, like that from a Fax machine, or Modem before it sends.
This was a call from my gas company (which is a branch of Sempra) providing an automated reminder of my appointment and letting me know that the gas company technician was on his way.
This number is a central number (automated operator) for Sempra Energy, the parent company of Southern California Gas Co. and San Diego Gas & Electric. You would use this number if trying to reach a person or department at either utility but don't know their direct number. (posted by an employee of SoCalGas)
I called back and it asked if I was looking for a Sempra employee. The reason I got this call is because my gas was disconnected due to home fumigation and is getting re-connected so they are calling to verify my appointment. Thanks Sempra!