The access control system
2-9
This layout uses a 4232 Comms module at the head of each branch.
These Comms modules talk via one 4230 or 4235 Comms module to
the PC.
Systems using host computers running software other than the Cotag
Access Control Software can use the same structures but may be
subject to different limitations.
Other structures arise when using 4232 Comms modules to extend
the physical size of the system either over line lengths greater than
1km or over more than one site via telephone lines. The chapter on
the Communications module discusses these techniques in more
detail.
Hardware Systems
If you are using the Cotag Access Control Software, each set of
controllers linked to a PC is called a “Hardware System”. You can
have more than one Hardware System connected to a single
computer, or to any of the computers on your local area network.
Local Hardware Systems
A Local Hardware System is a set of controllers which is always on
line and communicating with the host computer. Each Local
Hardware System communicates with the computer via a piece of
software called a “Comms Driver”.
Remote Site Hardware Systems
A Remote Site Hardware System is a set of controllers which only
communicates with the host computer when it is connected via a
normal dial-up telephone line with a modem at each end. The host
computer is configured to make contact with the controllers at the
remote site by dialling out at specified times, or after specified events.
The controllers at the remote site can dial in to the host computer
when an alarm occurs, or when the transaction buffer in a controller
is becoming full. Each Remote Site Hardware System communicates
with the computer via a piece of software called a “Modem Driver”.
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