On 01/08/2013 14:31, Andrew May wrote:
On 01/08/2013 08:08, Nightjar wrote:

For flats, I would have thought that the best option was a good quality
electronic key pad system, as I had on an office I used to rent. Each
tenant had their own code, which opened both their office door and the
common door (which could also be released by door phone). The landlord's
agent had to approve each code, so that there were no easy to guess
codes, and programmed them into the system. The multiplicity of codes
meant that none of the keys on the common door pad would show signs of
more use than others.


Which is fine for a small number of offices but as the number of codes
goes up the chance of randomly guessing a correct code goes down.


With a six digit code, you have a million possible choices. Even if
there are 100 flats, it is going to take a lot of random guesses to find
one code. Then you need to find which of the 100 flats that opens.

Colin Bignell