SmartSensor HD - Interprovincial Traffic Services

96 APPENDIX • SMARTSENSOR HD USER GUIDESmartSensorConnectorPowerWiresRS-485WiresNull Modem CableORDTE Device (PC)Straight-through CableFigure D.1 – Direct Serial ConnectionsDCE Device (Modem)NoteIf you do not have the right type or RS-232 physical connection you will not be ableto connect using the SmartSensor Manager software. Since null modem cables andstraight-through cables look similar, you may want to label them. Alternatively, youmay want to use a null modem adapter instead of a null modem cable. If you do,you can turn your straight-through cable into a null modem cable by attaching theadapter on one end.If you wish to connect the 9-conductor cable’s RS-485 wires directly to a PC or modem,this will require that these devices natively support RS-485 communications. Often, modernpersonal computers do not support RS-485 communications and support USB communicationsinstead. If your computer only supports USB communications, you may wantto use a Click serial to USB converter to make a direct connection.Appendix E - Signaling DelaysSignaling delays vary depending on what equipment is used. These delays may affect decisionsabout where to install the sensor in relation to other equipment in cases where timelinessin communication is necessary. The following is information about SmartSensor HDsignaling delays.Total signaling delay from front of vehicle = sensor delay + communications delay + contactclosure delay, where: