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System Network

The prototype system used a simple network of 4 digital signals to send keying information from the radio interface to the display units.  This was a limiting rsfactor to future expansion.  

A RS-485 full-duplex network has been designed to overcome the 4 zone limitation of the demo system.  It also allows sharing of information between display units, including the ability to display the count of people in a restricted zone.

Display units are daisy-chained from the radio interface enclosure (more on this in a moment) using CAT5 cables with RJ45 connectors.  The radio interface (master) uses one pair of wires to send keying information to the display units(slaves).  No other devices transmit on this on this pair of wires, so the keying signals will be reliably received by all of the display units.

The second pair of wires is used to send data from the display units(laves) to the radio interface(master).  For example, suppose a technician was cleared into zone A at one of the stations.  That station will transmit A 1 to the radio interface.  The radio interface will transmit the same message out to all of the display units where it may be acted upon if desired.  The station that send the A 1 message will listen to receive the message to verify it was sent out within a prescribed time and if not, it will send it again.  When a zone is clear of all personnel, a message - A 0 in this case - will be sent to clear all units monitoring zone A.  This communications scheme bring great power to the RID system to display and use the available information.

One notable thing this makes possible.... Currently, remote units are tied to one display unit.  With this communications system, a remote unit could be made into an RS-485 unit, and it can display the status of all zones; this might be handy display in a manager's office for example.

Network Concentrator

2/21 Update - The standard RID Radio Interface will support 16 radios and adds an 8 channel data concentrator in the same enclosure.

RS-485 networks must be daisy-chained, and end with a terminator.  Star arrangements and stub connections are not allowed.  It may be difficult to run one cable from the radio interface to all the devices in the control tower.  For this reason, we've developed a network concentrator.  Wires from each display unit may be home run back to the radio interface, or several different "networks" may be daisy-chained from the network concentrator.  Operation of the concenrator will be transparent to all units.

Operational Philosophy 

The ability to share information between units and to let people be cleared in or out of zones raises some operational questions.  It's my believe that one Air Traffic Controller is strictly in control of a zone.  This seems like a safety issue so that the security of a zone can be known. How information is shared between display stations and what control is permitted between stations.  The Clever4Hire RID system is all operated by microcontrollers; nothing is cast in stone.  How the pieces interact is simple to change by changing the software.  As the system evolves, the software can change as required.

A note about zones

The prototype system was based on existing RID systems which have 4 zones.  This new network model allows for 8 or even more zones.  This system is a development over the last few days.  Some changes will be needed on the display units will be required to support the additional zones available.  More information on this as it develops.


Network Configuration - Updated 2/21/2017

Ideally, the RID Radio Interface will be located in the rack with the radios or in close proximity.  Locating it remotely from the radios is not desired and may lead to false keying signals.



The revised Radio Interface will support 16 radios and has a built-in data concentrator to support up to 8 RS-485 network chains.  Chains may consist of a single device (home run wiring) or of a number of devices connected in a daisy-chain.  The practical limits of each chain are around 256 devices and 4000' of cable, so this should not be an issue in any installation.





An alternative arrangement, which will be helpful if cabling to the radio room is difficult, uses a remote concentrator.  One CAT5 cable is run between the RID Radio Interface and the concentrator and devices connected directly to the concentrator or in daisy-chains.  The concentrator will support eight RS-485 chains.


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