Micro switch works well

Mike, re your locks article, you may recall I sent your our proffered door lock setting and unsetting design for DD243 back in October last year ... the time when you were making such a fuss about single room lockup type properties.

The use of a final set lock and an intermediate contact on the door is pretty much our standard method of alarm installation (we note that the prox keypad is frowned upon by the ABI).

You have also highlighted the problem installers have with shunt locks and in particular UPVC doors. The secret is not in mastering installation of a shunt lock but to replacing the keep. Quite simply, replace the existing mortise keep with a manufactured keep with a built in micro switch. This is a very low cost minimum labour alternative.

Now with regard to the UPVC door, these have a multi point locking system but once again a humble micro switch installed within the lock keep works well. I concede that the alarm sets as soon as the handle is raised but if our clients forget to turn the key that cannot be the installer's problem. Both of these systems allow for wires to be easily concealed (we wire from the door contact) and UPVC doors collapse at almost any other point than the locking system so no danger of a size 9 key defeating this.

I would stress the point that as a company we install shunt locks and I am referring in particular to the pvc door situation. As I say, these cannot be kicked open releasing the lock but collapse the door at the transom or middle panels.

The same applies to aluminium doors, only we have an alternate method for these involving the use of a simple solenoid and external dallas key.

Ps ... Dantech manufactures a keep for normal mortise replacements and this can easily cope with the size 9 key in the same way tube and batten does. As in most things if installed professionally, impending litigation is not likely.