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Sourcing a Suitable Alarm Filter

Installer Q & A

It's not so much that there's suddenly a problem, it's more that your customers who have had a monitored alarm panel installed some time ago may have since upgraded to broadband. If they have and the alarm spur is not correctly filtered then the data portion of the broadband (ADSL) signal may stop the digi (dialer) from calling out in an emergency.

You need to ensure that there is a filter fitted between the telephone line and the "line in" conection to the dialer on the alarm panel.

There are options in terms of filters available and method of connection. Some installers have been known to take a standard ADSL filter and chop off the conenctors with cutters and hard wire the filter across the panel. But a standard ADSL filter doesn't have the protection that an alarm filter has (or should have) and it doesn't have any ability to seize the line. The filter used in the vast majority of locations acreoss Europe is the The APF7. It is a screw terminal filter, so the fitting is fairy simple for an alarm engineer. You just fit it in-line between the incoming telephone line and the alarm panel in it's simplest from. But for full functionality and to meet the requirements of EN50131 you should connect the filter "first-in-line" in the premises to achieve "line-seizure"

OK, well even on a simple telephone line the alarm panel should be conencted "First-in-line" that is why there are in and out connections on the digital communicator (digi) or dialer in the panel. It's just a pair of relay contacts inside which in an alarm state pull apart to disconnect any other telephone from the line. So to achieve it you need to route the incoming telphone line through the alarm panel first and then off to any extensions around the premises afterwards.

In a broadband (ADSL) installation you dont want to physically cut off all of the subsequent premises wiring with a pair of relay contacts. You don't know what your customer has or plans to have connected to the broadband line. Let's say for example that he plans to have a security webcam installed at a a later date. It won't be much use if your panel cuts it off as soon as there is a break-in.

The APF7 uses some internal electronics which when connected to the original relay contacts of the digital communicator (digi) in the alarm panel just disconnect the voice element of the broadband signal allowing the computer and data to keep working but allowing the panel full control to dial out.

The APF7 has been around for about 4 years. It has been successfully installed in tens of thousands of premises across Europe the UK being the largest installer at this time but that's because of awareness of the problem and awareness of the product rather than the need to install it anywhere else.

That really depends how far you want to take it. The fact is that any number of your customers may have upgraded to Broadband (ADSL) since you installed their alarm system and will have this problem without knowing. So, you should contact your customers and find out if they have had Broadband installed since the alarm panel was fitted. Another great point with the APF7 is that it will work quite happiy if it is fitted to a standard analog telephone line. So, from now onwards, if you install a new system and you fit one at the time, even on a non-broadband installation you can assure your customers that their installation is "Broadband Ready" and they don't need to call you out again if they decide later to upgrade to Broadband. Similarly, you can offer all of your exisiting customers an upgrade to make their systems "Broadband Ready" even if they don't have it today.

The APF7 was defined and specified by a company in the UK and is available to installers across Europe.

Click on the "Sourcing a Suitable Alarm Filter" link to the left for details.