Perle Systems Application Note
DOT Easily Adds VMS to Existing Network
The Department of Transportation (DOT) in a large metropolitan city was already using Perle Device Servers in order to Ethernet enable traffic controllers. The DOT began using Perle IOLAN Device Servers (DS) several years ago, to incorporate video surveillance technology at intersections. Perle IOLANs had allowed them to maintain the use of existing traffic controllers when they upgraded the network to a bandwidth for new video technology. At that time, the DOT was not only able to avoid new hardwiring and associated construction costs, but also the costs of replacing controllers that had not reached the end of their useful life.
Now the IOLAN Device Servers would be used for yet another essential function.
Electronic Variable Message Signs (VMS) have become a familiar sight on the arterial roads throughout many countries. VMS provide traffic management professionals with a reliable, fast, and effective means of communicating important traffic information to motorists. A wide range of details such as road conditions ahead, travel times, road construction details, accident information and AMBER Alert messages, can be displayed - all in real-time. This information, when relayed to motorists helps to reduce congestion and keep traffic moving efficiently and safely.
On the advice of a Traffic Consultant, the system had been configured with the scalability to accommodate future expansion. Now that the area required a VMS, it was easily connected; especially with Perle’s universal, software selectable EIA/RS232/422/485 serial port interface. This Perle advantage means that a single multiport IOLAN unit can support RS232/422/485 connection types in a software configurable per port setup. This eliminates the requirement for multiple device servers for each of the RS232/422/485 devices. With Perle’s software control for RS232/422/485 the potential for failure as a result of someone inadvertently flipping a switch is eliminated. Any serial device can be connected back to the Traffic Control Center (TCC) application in a TCP/IP format or converted back to serial format at the TCC depending on the application server’s requirement. Pavement sensors, PTZ cameras, vehicle counters, traffic controllers, or in this case - variable message signs - are easily and economically added. Perle IOLANs offer a wide range of 1-48 ports for maximum scalability and expansion.
Perle IOLANs are designed specifically to meet the rapid polling environments found in traffic management systems. With its 87 MIP processor, IOLANs have the lowest latency of any serial to Ethernet conversion product on the market. Flexibility and high performance IP technology, make the IOLAN ideal for critical ITS applications that require an efficient way of communicating with serial devices over a network. Initially, at the testing stage of this project, several Perle competitors failed to meet the stringent low latency solution requirements set by the DOT. Traffic control professionals that have to ensure safe and efficient surface transportation depend on the reliability of Perle IOLAN Device Servers.
Perle IOLAN Serial to Ethernet for ITS
- Low packet latency of 2 ms
- Meets NTCIP specifications
- IOLAN SDS1-T, SDS2-T and SDS4-T models all meet temperature range specifications of NEMA type 170 traffic controllers
- High performance processors in the IOLAN STS8 (400 MIPS) and SDS1 T (87 MIPS)
- Universal software selectable RS232/422/485 serial ports
- Wide choice of RS232 serial port interface models - DB9M, DB25M, DB25F and RJ45
- Serial packet data control - tune how serial data is forwarded across an Ethernet network