VOIP (Digital Phone or Vonage) and Security Systems

What is Voice over IP (Vongae, or Digital Phone), and how if affects your security system

VOIP is an acronym for Voice Over Internet Protocol. It simply uses your broadband internet connection to place voice calls digitally over IP based networks. Generally, a consumer will pay a flat monthly fee for local and long distance calls, often for considerably less than a regular analog land line.

Using VOIP And Alarm Systems Can Pose Problems Because:

1. An alarm system is designed to send its signals over an analog phone line. To transmit emergency signals properly using VOIP, the signal must be converted to digital, then converted again to analog. It is during this conversion that problems develop. Usually the signals arrive at the central monitoring station with errors, or not at all.

2. Your alarm panel comes equipped with a back up power supply in the event of a power failure. Because traditional phone lines will still work even if your power is out, your monitoring station will still receive the proper signals. With VOIP, your phone service (specifically your IP router and/or modem) will not operate during a power failure, preventing any kind of signal transmission from your alarm to the monitoring station. You can prevent this with the purchase of a UPS (Un-interruptable Power Supply) for your PC.

3. VOIP services tend to be more prone to “mysterious” technical issues and dropped calls. Your alarm panel may be communicating vital data to your monitoring station, and a dropped call will obviously interfere with this. Or, your alarm’s signal may go through without a problem on one attempt, but will fail on another for no apparent reason.

4. Similar to a land line, your VOIP line (specifically your cable connection) can be cut or disabled by a potential intruder, severing your link to the monitoring station.

An Overview of Alarm Signaling over POTS

Without focusing on a specific alarm protocol, here is what should happen when most popular DTMF protocols are used.

When an alarm event occurs, the panel will go off hook and “grab” the phone line. The panel will dial the DTMF digits of the pre programmed primary telephone number and wait until the alarm receiver answers the call. Upon answering the call, the receiver will play what is known as a handshake. This would normally be either a single high pitched tone or two very rapid, short, high pitched tones.

When the panel hears the handshake, it will start to send its first message as a series of DTMF tones. These tones are detected by the alarm receiver and checked at the end of each sequence. If the message is valid, the receiver will play what is known as a kiss-off tone. This is usually a single high pitched tone of up to one second in length.

On hearing the kiss-off tone, the panel either sends the next signal in the queue, or it hangs up – happy in the knowledge that its message has been sent and accepted.

Enter Voice over IP

After decades of signaling alarms over POTS, the major Telco’s recently started to tell us that VoIP will increasingly replace circuit switched communications as the preferred method of communication.

Many in the security industry thought that the analogue terminal adapters (ATA’s) used by the VoIP world would provide a quick, low cost method of signaling alarms over the internet. After all, if two people could talk over the internet using ATA’s in the same way as they talk over a traditional phone line, then surely an alarm panel should be able to talk to an alarm receiver in much the same way as it has always done.

Unfortunately, even after a certain amount of success in some tests, this has proved not to be the case. Somewhere between converting analogue into digital, traveling over the wire and converting digital back to analogue, things like noise and latency are introduced and along with other audio problems associated with VoIP networks, can cause alarm communications to fail.

Security system monitoring must work every time and with the inconsistency of VOIP phone service we recommend the GSM unit for wireless system monitoring. This removes the risk of the devices possibly not working in an emergency.