FAQs
I have a case where a communicator sent a signal into my central station's receiver and the NOC website shows that the receiver kissed-off the signal, but the signal was never processed by the automation. What would cause this?
Central Station alarm receiver technology has advanced over the years and receivers are available today that tout the capability to support multiple formats decoded on the same line card and can tell the difference between one format and another. Unfortunately, POTS communication and other POTS replacement technologies have actually degraded due to noisy copper telephone lines not being fixed by the carriers and POTS replacement technologies are occasionally impacted by high network traffic and other packet loss problems. The net result is that the DTMF tones delivered to the receiver could be garbled or corrupt or missing digits. In the case of a receiver that supports many formats, the receiver may determine that it has received a valid format if it sees enough digits and was presented with the right handshake tone -- although it is wrong. A 16-digit CID format reduced by the receiver to 8 good digits may yield a wrong alarm delivery but appear to be a valid 8-digit-format. This corrupt signal may be erroneously kissed-off by the receiver as a valid signal that can never be processed and will result in a missed alarm signal.
Sur-Gard has recognized this issue and, as shown below, cautions central station engineers to ensure the handshake sequence is correct to avoid problems--but this does not necessarily prevent garbled data from being misinterpreted. Especially at risk are Contact ID formats sent to a receiver line card that also supports 8-bit formats--because they both use the same 1400 Hertz kiss-off tone. In that case, if some number of the CID digits are not read, but 8 digits of valid data are read by the receiver, the receiver misinterprets the data as an 8-digit format and will respond with the correct kiss-off tone, thus causing the alarm panel transmitting the alarm to incorrectly believe it has delivered the alarm message correctly.
We strongly urge our Dealers to ensure that their central station does not have 8-digit DTMF formats enabled on the same receiver line card that is receiving CID formats. In fact, Sur-Gard has provided the ability to disable 8-digit formats (shown below) using option 16. For other receivers, please consult with the documentation supplied with that receiver.
NAPCO has worked with several central stations who recognized this issue not only from alarm messages delivered by NAPCO but also delivered by other alarm control panels. For those using Sur-Gard System III receivers, configuring option [16] bit 03 (to eliminate 8-digit formats) has solved the issue. Dealers have also simply directed Contact ID communications to line cards that do not have 8-digit formats enabled.
Option [16]: Format disabling Option - Default [00]
This option is bit oriented and will disable the decoding of the following DTMF formats. For multiple formats, all corresponding bits must be disabled. Example: To disable 13, 22 and 23 digits DTMF formats, set option to 4A.
Bit 01: 15 digits DTMF formats
Bit 02: 13 digits DTMF formats
Bit 03: 8 digits DTMF formats
Bit 04: 22 digits DTMF formats
Bit 05: 11 digits DTMF formats
Bit 06: 12 digits DTMF formats
Bit 07: 23 digits DTMF formats
