diy door entry system help

[Misterque]

Hi, I'm looking to install an audio door entry system in a block of 4 flats. There is currently no lock. We would prefer to install a maglock but cost is an issue (there's a landlord who hasn't been burgled twice, unlike my friend, and who won't pay to have a system professionally installed).
I'm fairly technically minded but haven't done anything like this before. All advice - what systems are best / cheapest, where to buy, lists of exactly what I'll need - gratefully received. From what I've read so far, I'm not sure how entry is usually gained from the outside when a maglock is installed.
Thanks.

 

[ColJack]

panel on the outside with 4 buttons, one for each flat..
handset / box on wall rings in whichever flat you press..
owner speaker to person outside via intercom.
owner presses button and releases the maglock..

http://www.tlc-direct.co.uk/Products/DSDK4.html

best to use a door lock rather than a mag-lock..
that way you can have a fail secure one and still use keys for the owners to get in and a thumbturn to get out..

if your friend is the one getting burgled, then I'd suggest that they beef up their own security as well..

 

[Locksmith]

Mag locks are low security, use a system as stated above, thumbturn cylinder and electronic striker plate controlled by intercom and maybe an electronic keypad on the outside of the building.