The ACS Access Control System offers companies supplying access control systems for a robust and inexpensive campuse wide communication solution. Implemented at a site spread over 25 sq. km., with 1 remote site accessed using modems, ACS is a safe and tested solution ensuring redundancy at all levels.

The system consists of :

a. 2 communication servers ( CS ) - they are in a redundant configuration such that if one system stops functioning, the other takes over smoothly. They get the weekly user access database from the Data Collection Server. This database consists of the access options for each employee for the week - where he can come in, when is allowed inside, can he go outside without permission, etc.

b. 15 cluster control PCs ( CC ) - these are 386 based motherboards with a Solid State Floppy Drive. 2 RS 485 ports are available, one for connectivity to the Communication Servers and the other for communication to the card readers.

c. Card readers - Each cluster has 16 readers in a cluster, connected on an RS 485 bus to the CC. Every card reader has a turnstile which needs to be released when a swiped card is validated.

d. Special clusters - A set of 6 readers were connected to the CC using a modem, using an existing telephone link.

Platform :                                             DOS
Development Package                         Turbo C/C++ for CCs and CS software
                                                            Assembler and C for ( 8051 ) for the Card Readers

Scope of the project

a. Modification of firmware on Card Readers to support :

RS 485 communication with poll by CC
Addressing of each reader
Logic changes to ensure no data erasure without a valid command
Interrupt to the CC if case of E2PROM overflow

b. Design / Development of the Cluster Controllers :

Selection of platform - 386 based SBC was selected
Development of Solid State Floppy Drive Card
Communication with Card Readers 
Communication with the Communication Servers ( CS )
Communication to Special clusters through modems

c. Development of Software on the Communication Servers ( CS ) :

Inter CS communication to ensure redundancy
Communication to CCs to collect status
Communication to the Data Collection Server ( DCS )
Maintaining the User Access Database - who is allowed where and when
On-line updation of User status and transimission of the same to the CCs
Updating on-line information to the DCS.

Special Features

• Handles large loads effortlessly - 6000 users pass through 14 readers within 15 minutes

• Anti-pass back facility implemented - within 1.4 seconds of a user walking through the reader, all CCs are alerted of his entry, preventing another user from walking in using his card

• Zero loss of data - the entire software structure is such that only when the upward data transfer is successful, the lower segments will erase their data

• Extremely simple solution - based on low cost 80386 SBCs and DOS. The CSs were 486-100 MHz based PCs