Issue | U.L Listed (DOYLE) | Non-UL Answering Service |
| Operators on Duty | U.L. mandates the number of operators on duty per shift | No requirements. Most have only one, especially in the late evening/early morning. |
| Power Outages | U.L. mandates an uninterrupted power supply without power equipment. | No requirements. Could be without power indefinitely and unable to receive alarms |
| Types of Communications used | U.L. requires 2 types of communications to contact emergency response authorities. Doyle Uses: - standard telephones
- direct ring supervised leased line
- cellular network
- long range radio network
| No requirements. Most use standard telephone lines only. |
| Response Center Building Security | U.L. mandates that Response Center be protected from fire and intrusion, including specifying what materials the building is constructed from. | No requirements. Many are homes or offices. |
| Test Signals | U.L. requires that 24-hour test signals be transmitted. | No requirements. Most are still not computerized. |
