Access Control & Attendance

Access control and attendance systems govern who may enter, record when they do, and produce the statistics management needs — while doubling as an intruder deterrent. They integrate with other building systems and with HR and payroll.

Power — size the supply with headroom, prefer linear power supplies, and feed locks and controllers from separate circuits. Mount power supplies as close to the load as practical to avoid interference and voltage drop.

Cabling — keep power, communication and signal cables in separate routes, with at least 20 cm between power and low-voltage conduit. Use multi-strand cable of adequate cross-section for power; use shielded category 5 twisted pair for signal and communication, with the RS-485 bus on one twisted pair for A+ and A-. Four-core shielded cable of 4 x 0.5 mm is a sensible default.

Cabling rules that are easy to get wrong: never use the shield as the 0 V return; each shield segment may be earthed at one end only; if a segment cannot be earthed, bond the shield to the next segment; tie the signal grounds of all modules together; solder and insulate any break in a run; keep network cable away from mains cable; and add a repeater beyond 1,200 metres, which extends the run by a further 1,200 metres.

Readers — do not mount on metal, keep at least 30 cm between two readers, and power them from the controller where possible. If a reader needs its own supply, use a linear regulated supply and never connect the DC negative to mains earth.

Locks — a magnetic lock must sit flat and tight against its armature plate, otherwise holding force drops. For electric bolt locks, drill the strike hole deep and wide enough for the bolt to seat fully; a partially seated bolt chatters and draws continuous current, and the lock body overheats.

Controllers — use one supply for controllers that are not isolated, connect network adapters to controllers in a daisy chain, and site equipment away from sources of electromagnetic interference.

We survey the doors, specify the hardware, install and commission, then hand over the access rules, attendance reports and a maintenance schedule.