New Search
City's existing Model 170 traffic signal controllers would require the installation of an Ethernet - <br />enabled modem card to utilize Ethernet over copper communications. <br />_ Analc j <br />CU <br />Ca,uera <br />Contrn.Ver Cabinet <br />l Ettterret- Enabled <br />, <br />I <br />I Mndem Card <br />Encoder <br />I <br />i <br />��i <br />I <br />a I <br />m <br />V <br />u I <br />U <br />`db� <br />I <br />I _ <br />1 ®�:� <br />I <br />I i <br />EVtarnet I <br />170 Traffic <br />Access I <br />I signal Controller <br />-------------------- <br />Dmce <br />Netveoek Nun <br />I <br />I <br />I i <br />I <br />7tivated Parr Go1,pet <br />Access <br />I Device Central Server <br />I <br />Figure 6. Ethernet over Copper Example <br />4.3.2 Fiber Optic Cable <br />Fiber optic cable has become the preferred physical plant medium for transportation <br />communication networks for a number of reasons: <br />• A single fiber can carry very large bandwidth. <br />• There is low signal loss, which means signals may be carried long distances without <br />repeaters. <br />• Fiber optic cable is less subjective to electromagnetic interference (EMI) than copper <br />cable. <br />• Fiber optic cable furnish costs are comparable to twisted pair copper cable, but support <br />much higher bandwidth capability. <br />• Transmission systems for video signals are cost effective. <br />Fiber optic cable may be used two ways within the traffic network: direct connection or network <br />connection. <br />Direct Fiber Optic Connection <br />Similar to FSK over copper, fiber optic cable may be run directly between a modem in a <br />controller cabinet to a modem back at the hub as shown in Figure 7. Under this scenario RS- <br />232 data is transmitted between the modem and its target network device (e.g. traffic signal <br />controller or central traffic signal system server). The primary disadvantage of a direct fiber optic <br />' cable connection is that it does not provide an alternate path back to the network hub which <br />could result in all communications being lost if the cable is cut or damaged. Additionally, direct <br />connections require the installation of more fibers to support all of the devices on the network. <br />' DKS Associates Eugene Master Traffic Communications Plan March 2008 <br />Page 22 <br />