Monitored alarm systems (alarm panels with a modem to dial up the monitoring centre) have often posed a small headache for alarm installers and ADSL installers alike.

It's usually part of your service agreement with your alarm company that the alarm is permanantly hardwired to the telephone line. Understandable, or else the alarm could be accidentally (or deliberately) disconnected from the line all too easily. Here's an excellent device to solve the Problem With Alarms...

On this page...
Overview
Physical details
Wiring
Beyond alarms - plenty of other applications
BUY your hardwire-only alarm filter linebox(s)



NOTE: If you want to know more about WHY ADSL filters are necessary at all, read THIS article



Overview
Every standard telephone device needs to be filtered when ADSL is operating on the phone line. This includes alarms which dial up to monitoring centres, because they're just using a little telephone modem to do it. If you don't pass the alarm through an ADSL filter, it interferes with the ADSL operation, causing failed connections and shitty data rates - but worse still the ADSL may well prevent the alarm from communicating with the alarm control centre.

Now, there's no doubt about it that alarm panels NEED to be directly hardwired to your BT line one way or other. It's just not on to have it plugged into a wall socket. Anybody can just reach out and unplug that, so that's what we in the trade call "silly".

Side note - Elsewhere on this site you'll find discussion of incorrectly/illegally installed alarms which the installer's hardwired to the back of the BT master socket *tut tut!*

So here's a completely enclosed microfilter unit, with ONLY hardwire connections - screw terminals for both the supply wires in, and for the alarm panel wires out.




Physical details
The unit is cleverly built onto the back of a Full Blanker as used in our range of modular telephone/communications fittings. A small side benefit of this is that you could happily use it in a "quad" modular faceplate along with two modular sockets or your choice (RJ45, RJ11, BT phone sockets, for example) if your plans call for it.

It's supplied as pictured here, consisting of three physical parts: The faceplate, which is one of THESE, the microfilter module, and a surface mount back box. Although supplied as a ready-to-fit surface-mount assembly, you can also happilly flush-mount it too, assuming a suitable depth of flush-fitting patress is fitted in the wall.

SIZES:
The faceplate and modular filter unit is 85x85mm, the standard UK single "1-gang" electrical/telephone wall box size

Depth of the assembled unit including surface-mount backbox is 25mm. If you intend to flush-fit, then allowing for the microfilter unit and wiring, we'd advise you to use no less than a 20mm recessed pattress.




Wiring connections
The terminals are a pair of 3-way screw terminals

The line input (connect the raw, unfiltered phone line here) requires only wires 2 and 5 of the phone line, (although wire 3 can be connected for here for neatness, it isn't actually used by this device - it generates its own ringer signal for the output terminals).

The ADSL-filtered line output (to the alarm panel or indeed to ANY secondary telephone extensions or devices downstream from this box) provides wires 2, 3 and 5, now with the ADSL signal cleanly separated and removed.




Beyond alarms - plenty of other applications...
This was designed primarily to help with a professional and correct installation of an alarm panel in conjunction with an ADSL-enabled line, where the cable supplying the panel is not already ADSL-filtered. There are of course a great many uses beyond simply alarm work. For example, certain circumstances specific to your case might indicate that hardwiring-only, with no socket access, might be preferable for security reasons.