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I <br />I <br />I <br />I <br />I <br />combination of Clackamas County -owned and ODOT -owned cable plant. Due to a <br />limitation in the existing traffic signal system, the County has maintained the copper <br />plant to traffic signals within the corridor, but uses fiber modems to transmit the traffic <br />signal data from a field hub to the TOC over fiber optic cable. The County has a fiber <br />optic connection to ODOT and the City of Portland central traffic signal system via a <br />shared metropolitan area fiber network. Ultimately, the County intends to install <br />additional fiber optic cable and migrate all field devices, including the traffic signal <br />controllers, to the Ethernet network. <br />City of Vancouver (Washington): Vancouver has installed an extensive Ethernet <br />network to field devices using a combination of fiber optic cable and Ethernet over <br />copper. The majority of the previous copper plant in the City has been replaced with fiber <br />optic cable, new traffic signal controllers are purchased "Ethernet- ready ", and the City is <br />expanding their use of video cameras using the existing Ethernet network operating to <br />the traffic signal controllers today. <br />City of Roseville (California): Roseville is using Ethernet over copper for their entire <br />network of traffic signals, system detectors, and CCTV cameras and is posting <br />streaming video and congestion information on their website <br />( http://traffic.roseville.ca.us/roseville/ ). <br />4.3 Communications Technology Options for Eugene <br />In order to select a network architecture best suited for the City's traffic needs it is important to <br />consider the available technology options that best meets those needs. This section includes a <br />description and evaluation of the following technologies: twisted pair copper cable, fiber optic <br />cable, wireless, leased services, and hybrid. <br />4.3.1 Twisted Pair Copper Cable <br />As described in Section 2.1, Public Works has made significant use of twisted pair copper cable <br />throughout the City to communicate with 85 percent of their traffic signals and four CCTV <br />cameras. The most significant drawback of twisted pair plant is the narrow bandwidth it can <br />provide. Additionally, the City's existing plant does not have much spare capacity (e.g. spare <br />pairs or excess bandwidth) to support additional traffic signals and devices. There are two <br />options for utilizing twisted pair copper cable as part of the communications network: FSK over <br />copper or Ethernet over copper. <br />FSK over Cooper <br />The frequency shift keying (FSK) communications protocol may be used with twisted pair <br />copper cable for low speed data transfer up to 19.2 kbps. FSK modems utilize a modulation <br />protocol to convert digital data from a computer to analog data that may be transported over <br />twisted pair copper cable or telephone lines. The City currently uses one FSK modem in each <br />traffic signal controller cabinet and another FSK modem, which may support several controllers, <br />back at the network hub to allow RS -232 traffic signal data to be transmitted on twisted pair <br />copper cable between each traffic signal controller and the central traffic signal system server <br />as shown in Figure 5. Other ITS devices such as dynamic message signs (DMSs) may also be <br />supported by FSK over copper. Although FSK modems do not support CCTV cameras, other <br />analog modems are available to transmit CCTV data over twisted pair copper cable similar to <br />the FSK modem example shown in Figure 5. <br />' DKS Associates Eugene Master Traffic Communications Plan March 2008 <br />Page 20 <br />