So what did we do. I used to use a relay type system in 2007-10 in my
previous data centre life. It¹s pretty good but a bit ³industrial². It¹s
also so 2007 (even 1990) and doesn¹t scale well when you are trying to do
3,000 racks and 6,000 doors per facility.
Part of the scaling issue was the door locks on that system were conventional
solenoids, which from memory needed about 1A @ 12VDC to fire. If a customer
had 30-40 racks (and a couple did in that facility), you'd need to potentially
fire 60-80 doors, or need 60-80 amps available (I have a recollection we used a
12V SLA battery to ride out those peaks). Additionally, monitoring lock status
would have needed separate wiring and separate inputs. Cabling was a star
topology (each rack directly back to the controller).
The TZ locks use a fraction of that power - from memory, only a few amps to do
a pod of 30 or so racks. Firing a lock is measured in milliamps, not amps.
The locks are controlled over RS485, so you get lock control and monitoring
over a single cat-5. From memory the cable topology is technically
hierarchical, but you could loosely consider it to be a bus. Overall, vastly
superior to the 'industrial' style system.
I looked at the APC electronic
locking system, but the big issue is that some fool in product decided to
remove radius authentication, allowing a decent independent
command/control capability.
At the time the available version of the product didn't deal with too many
racks, which also meant a lot of under-floor power outlets to feed the
controllers). I think they were coming up with a denser version, but I didn't
see it.
