|This report is an archived publication and may contain dated technical, contact, and link information|
Publication Number: FHWA-HRT-06-139
Date: October 2006
This NEMA standard excerpt is reprinted with permission of the National Electrical Manufacturers Association, 1300 North 17th Street,Suite 1847, Rosslyn, VA 22209. For further information, and to order a complete copy of the standard, visit www.nema.org
The following excerpts are provided from NEMA Standards Publication TS 2- 2003 v02.06, Traffic Controller Assemblies with NTCIP [National Transportation Communications for Intelligent Transportation Systems (ITS) Protocol] Requirements. TS 2-2003 v02.06 is a revised and reballoted version of TS 2-1998. Version v02.06 includes the revisions from TS 2 amendment 1 v01 and also includes minor revisions to sections 3, 5, and 6. TS 2-2003 v02.06 was balloted in January 2003 and approved by NEMA in May 2003.
NEMA TS 2-2003 is published by the National Electrical Manufacturers Association, 1300 North 17th Street, Suite 1847, Rosslyn, VA 22209. For further information and to order a complete copy of the standard, visit www.nema.org. NEMA TS 2 was developed and is maintained by the member companies in the NEMA Transportation Management Systems and Associated Control Devices Product Group.
This appendix is reprinted by permission from the National Electrical Manufacturers Association. Excerpt is © 2003 by NEMA. All rights reserved. For clarity, text in [square brackets] has been revised from the original.
The NEMA TS 2 standard expands on the older NEMA TS 1 Traffic Control Systems standard. The TS1 standard was based on the philosophy that controllers would provide a basic set of features and standard connectors. Manufacturers would compete based on the hardware and software they provided inside the controllers. The NEMA TS1 standard was successful for isolated actuated intersection control, but it lacked sufficient detail for implementing more advanced features, such as coordinated-actuated operation and preemption. Type 1 systems include the controller unit, conflict monitor, and the included features of each. Individual vendors supplemented the TS 1 standard by providing the complement of features necessary for deploying coordinated-actuated traffic signal systems. This introduced incompatibility and procurement issues, particularly when government agencies needed to upgrade existing signal systems at a later date and had to solicit competitive bids. Nevertheless, the competitive market forces continued to rapidly advance the state of the practice and created a following that led many States to adopt the NEMA standard. In the late 1980s and early 1990s, the NEMA TS1 specification was updated with NEMA TS2 to provide coordinated-actuated operation, preemption, and an optional serial bus to simplify wiring.(1)
The detectors, referred to as electronics units in other chapters of this Handbook, are described in the TS 2 standard by the following attributes:
These definitions reflect the consensus of the traffic control equipment industry as represented by NEMA and are intended to be in harmony with terminology in current usage, such as is published in the Manual on Uniform Traffic Control Devices and various technical reports of the Institute of Transportation Engineers.
The detection of vehicles on one or more intersection approaches solely for the purpose of modifying the phase sequence and/or length for other approaches to the intersection.
The ability of a vehicle detector to detect the passage of a vehicle moving through the zone of detection and to ignore the presence of a vehicle stopped within the zone of detection.
The ability of a vehicle detector to sense that a vehicle, whether moving or stopped, has appeared in its zone of detection.
A device for indicating the presence or passage of vehicles or pedestrians.
A detector that is capable of being actuated by vehicles proceeding in either of two directions and of indicating in which of the directions the vehicles were moving.
A detector that is installed in a selected location to detect vehicles which may not otherwise be detected and whose output may be modified by the controller unit.
A detector that has the capability of differentiating among types of vehicles.
A detector that is capable of being actuated only by vehicles proceeding in one specified direction.
A detector that is arranged to register actuations at the controller unit only during the green interval for that approach so as to extend the green time of the actuating vehicles.
A detector that senses radiation in the infrared spectrum.
A detector that utilizes a light-sensitive device for sensing the passage of an object interrupting a beam of light directed at the sensor.
A detector that senses a change in inductance of its inductive loop sensor by the passage or presence of a vehicle near the sensor.
A detector that senses changes in the earth's magnetic field caused by the movement of a vehicle near its sensor.
A detector that measures the difference in the level of the earth's magnetic forces caused by the passage or presence of a vehicle near its sensor.
A detector that is capable of being actuated by vehicles proceeding in any direction.
A detector that is responsive to operation by or the presence of a pedestrian.
A pressure-sensitive detector that uses a pneumatic tube as a sensor.
A detector that is capable of sensing the pressure of a vehicle passing over the surface of its sensor.
A detector that is capable of sensing the passage of a vehicle through its field of emitted microwave energy.
Any type of vehicle detector used to obtain representative traffic flow information.
A vehicle detector with its sensor located to one side of the roadway.
A detector that responds to sound waves generated by the passage of a vehicle near the surface of the sensor.
A detector that is capable of sensing the passage or presence of a vehicle through its field of emitted ultrasonic energy.
A term used to describe the operation of a detector channel output when a presence detection occurs.
The ability of a detector to continue its output for a predetermined length of time after the vehicle has left its zone of detection.
The ability of a detector to delay its output for a predetermined length of time after a vehicle has entered its zone of detection.
The sensor form that is commonly used with a magnetometer type detector.
The sensing element of a detector.
That area of the roadway within which a vehicle will be detected by a vehicle detector system.
[NEMA TS 2-2003] Section 2 relates to environmental standards and operating conditions for intersection traffic control equipment. This section establishes the limits of the environmental and operation conditions in which the Controller Assembly will perform. This section defines the minimum test procedures which may be used to demonstrate conformance of a device type with the provisions of the standard. These test procedures do not verify equipment performance under every possible combination of environmental requirements covered by this standard.
The Loop Detector Unit shall perform its specified functions under the conditions set forth in this Section. This Clause defines the test procedures required to demonstrate the conformance of a Loop Detector Unit with the provisions of the standards.
Loop detector units shall operate in accordance with requirements listed herein under the following environmental conditions.
Temperature and humidity shall be in accordance with 2.1.5.
Loop detector units shall operate normally when the test impulse described in 2.1.7 is applied as follows:
Detector loop inputs are specifically excluded from this test.
In the NEMA standard, tables and figures are delineated by a double ruled bar at the top and bottom of the table or figure. When the figure or table has notes at the bottom, the double rule is below the notes. This delineation is kept in this appendix for consistency with the standard.
Figure 2-4 TEST CONFIGURATIONS
The loop detector unit shall be capable of withstanding the eight nondestructive transient tests described in Figure 2-5. Each test shall be repeated 10 times with the loop detector unit operating from its normal power source. The time between repetitions shall not exceed 10 seconds.
The energy source shall be a capacitor, oil filled, 10 microfarads ± 5 percent, internal surge impedance less than 1 ohm connected in accordance with Figure 2-5. The voltage on the capacitor shall be adjusted as described herein. The test push button shall be activated for at least one second for each of the 80 test repetitions.
After the foregoing tests, the loop detector unit shall operate normally.
Figure 2-5 LOOP INPUT TERMINAL TRANSIENT TESTS
The Transient Test Configurations data are not listed as a table in the NEMA specifications. Therefore, for consistency they are not listed as a table in this appendix.
|Test Number||Test Selector Position||Power Supply Setting +5%||Polarity Selector||Load Across Detector Input||Tested Inputs|
|1||1||1000||Positive||None||D to E|
|2||2||2000||Positive||5 ohms||D to E|
|3||3||2000||Positive||5 ohms||D to L|
|4||4||2000||Positive||5 ohms||E to L|
|5||1||1000||Negative||None||D to E|
|6||2||2000||Negative||5 ohms||D to E|
|7||3||2000||Negative||5 ohms||D to L|
|8||4||2000||Negative||5 ohms||E to L|
|*The pin designations shown are for Channel 1. Similar tests shall be performed on all channels (i.e., pin pairs J and K, P and R, and U and V, respectively and as applicable) of the loop detector unit.|
The loop detector unit shall maintain both its physical integrity and operating characteristics after being subjected to the vibration test in 2.2.8. This test shall be run at nominal voltage and room environmental conditions.
The loop detector unit shall suffer neither permanent mechanical deformation nor any damage which renders it permanently inoperable after being subjected to the shock test described in 2.2.9.
This test shall be run at room environmental conditions without power applied to the unit.
[NEMA TS 2-2003 Section 6] defines the minimum requirements for auxiliary devices within the cabinet, consisting of solid state load switches, solid state flashers, flash transfer relays, and inductive loop detector units.
[In the] TS 2-1998 update of TS 2-1992, the SECTION 6 [was revised to include these changes in detector specifications:]
Detector Configurations has been modified to add four new types (AC, BC,CC, & DC) with communications port TX & RX capability.
Detection Outputs & Status Outputs condition has been added for the Disable and Reset states.
Detector Connector Terminations has been modified to add Detector Address Bit #3.
Clause 0 responds to the need for a series of Inductive Loop Detector Units which provide inputs for traffic-actuated or traffic-responsive control, surveillance, or data collection systems. The Inductive Loop Detector Unit responds to the presence of vehicles on the roadway by relying upon the effect of the conductive mass of the vehicle on the alternating magnetic field of a loop. When a vehicle passes over the loop of wire embedded in the surface of the roadway, it reacts with the alternating magnetic field which is associated with that loop. On standard loops this reaction is a reduction in loop inductance.
These standards cover the performance and design requirements of interchangeable Inductive Loop Detector Units. A Detector Unit used with a sensor loop embedded in the surface of a roadway detects vehicles moving or standing in the detection zone of the sensor loop. The output of the Detector Unit may be used directly to provide an input to a vehicle-actuated traffic CU or provide inputs to traffic-responsive control and surveillance systems. Detector Units generate outputs indicative of vehicles passing through the sensor loop zone of detection. This output may be used for counting (volume) or for detecting presence time representative of the time that vehicles are in the sensor loop zone of detection (occupancy), or both. When two loops are placed in a lane, one downstream from the other, the time between the sequential responses of detectors attached to these loops may be used to measure speed.
Electronic circuitry which functions as a Loop Detector System.
The adverse interaction of any channel of a Detector Unit with any other channel.
A term used to describe the duration and conditions of the occurrence of a detector output.
The electrical cable which serves to connect the sensor loop(s) to the input of the Detector Unit.
A vehicle detector system that senses a decrease in inductance of its sensor loop(s) during the passage or presence of a vehicle in the zone of detection of the sensor loop(s).
An electronic device which is capable of energizing the sensor loop(s), of monitoring the sensor loop(s) inductance, and of responding to a predetermined decrease in inductance with output(s) which indicates the passage or presence of vehicles in the zone(s) of detection.
A command for the Detector Unit to calculate a new reference frequency (the frequency that the loop oscillates at when no vehicle is influencing the loop) for the channel being reset and to appropriately adjust other channel related parameters.
A command for the Detector Unit to set all parameters to the states they would be set at if power had been applied at the moment the RESET command is received or released.
An electrical conductor arranged to encompass a portion of roadway to provide a zone of detection and designed such that the passage or presence of a vehicle in the zone causes a decrease in the inductance of the loop that can be sensed for detection purposes.
A system for indicating the presence or passage of vehicles.
That area of the roadway within which a vehicle is detected by a vehicle detector system.
The Detector Unit defined and described in this standard shall respond to changes in the inductance of the sensor loop/lead-in combination(s) connected to its loop input terminals. It shall develop a detection output when there is a sufficiently large decrease in the magnitude of the connected inductance.
The sensor loop(s) connected to the Detector Unit input terminals shall be located at the intended zone(s) of detection. The sensor loop(s) shall be connected to the Detector Unit by means of lead-in cable.
The sensor loop(s) shall be so configured that the presence of a vehicle in each zone of detection causes a sufficient decrease in inductance to cause an output response from the Detector Unit.
This standard covers Detector Unit configurations shown in Table 6-1.
|Rack Mount Detector Unit Type||NEMA Detector Unit Designations||Delay/Extension Timing||Communication Port RX & TX|
|2 Channel||Type A||None||No|
|4 Channel||Type B||None||No|
|2 Channel||Type C||Included||No|
|4 Channel||Type D||Included||No|
|2 Channel||Type AC||None||Yes|
|4 Channel||Type BC||None||Yes|
|2 Channel||Type CC||Included||Yes|
|4 Channel||Type DC||Included||Yes|
Each channel shall be provided with independent loop input terminals and shall deliver detection information on independent output terminals.
The Detector Unit shall be easily disassembled to gain access for maintenance. When thus disassembled, the Detector Unit shall be operational for trouble shooting.
All printed circuit boards shall be per 18.104.22.168.
22.214.171.124.2 Component Identification
All components shall be identified per 126.96.36.199.
Detector Unit DC Supply Voltage
This input supplies power. The current consumption shall not exceed 50 milliamperes per channel. The return for this input is Logic Ground as described in 188.8.131.52. This input shall not be connected within the unit to any loop input. The input shall draw a surge current not to exceed 5 amperes at the time of power application to the input. The Detector Unit shall not be damaged by insertion to or removal from a powered Detector Rack.
184.108.40.206.2 Low Supply Voltage Automatic Reset
A Reset Unit condition shall be activated anytime the input DC supply voltage falls below that which is required for operation, as defined in this standard.
A Reset Unit condition shall not be activated when the DC Supply Input falls below 10 volts for less than 0.25 milliseconds.
This input is the return for the Detector Unit DC Supply input. This point shall not be connected within the unit to AC Neutral, Earth Ground, or to any loop input terminal.
The loop Detector Unit shall have a terminal for connection to the chassis of the unit. This input shall not be connected to Logic Ground, AC Neutral, or to any other point within the unit, except that it shall be permissible to use this input as a return for transient protection devices.
If the unit has a metallic case or front panel, the case and/or front panel shall be connected to Earth Ground.
Control inputs shall have the following characteristics as measured from Logic Ground.
220.127.116.11.1 Low or Active State
A voltage between 0 and 8 volts shall be considered the Low or active state.
18.104.22.168.2 High or Inactive State
A voltage greater than 16 volts shall be considered the High or inactive state.
22.214.171.124.3 Transition Voltage Zone Of Input Circuitry
Transition zone of input circuitry from Low state to High state and vice versa shall occur between 8 and 16 volts.
126.96.36.199.4 External Transition Time
External transition from Low state to High state and vice versa shall be accomplished within 0.1 milliseconds.
188.8.131.52.5 Maximum Current
Over the voltage range 0 to 26 volts DC, the maximum current In or Out of any input control terminal shall be less than 10 milliamperes. The input circuitry shall be returned to the Detector Unit DC supply in such a manner that the removal of all connections to the input shall allow the voltage at the input terminal to rise to the High or inactive state. Rising to Detector Unit DC supply voltage is permitted.
184.108.40.206.6 Signal Recognition
Any input signal (including External Reset, Pin C) shall respond as defined in 220.127.116.11.3.
All channels shall remain in a RESET UNIT or RESET CHANNEL condition, see 18.104.22.168 and 22.214.171.124, while Pin C is held in an Active State (Low) voltage.
126.96.36.199.7 Activation of Delay/Extension Feature
The application of a Low state voltage to a Delay/Extension input shall function to inhibit the delay timing function and/or enable the extend timing function.
This input is provided for downward compatibility. (Authorized Engineering Information.)
188.8.131.52.8 Activation of Detector Unit Address Feature
The application of a Low state voltage to a Detector Unit Address input shall activate the input, e.g. it is a logic 1. Four address input pins shall provide for a maximum of 15 hard wired addresses. Address FF(hex) shall be a broadcast address.
The Data Receive input, RX, must have an input impedance 45 kohm to 105 kohm and an input capacitance less than 250 picofarads. This input impedance shall terminate to DC common. The input open circuit voltage shall be less than 0.9 VDC. The input shall be functional when voltages over the range of ±25 VDC are applied to it. The Transition Region is any voltage between a Mark and a Space.
184.108.40.206.1 Mark State (Binary 1)
During Mark, the RX input shall recognize as a Mark voltages less than 0.9 VDC.
220.127.116.11.2 Space State (Binary 0)
During Space, the RX input shall recognize as a Space voltages greater than 3.0 VDC.
18.104.22.168.3 Other States
The RX input shall not be damaged when connected to any voltage up to 26 VDC and:
22.214.171.124.4 Transient Withstand
The RX input shall not be damaged by application of the transients described in 126.96.36.199 through 188.8.131.52.
Two loop input terminals shall be provided for each sensor channel. These inputs shall be isolated (resistance > 106 and breakdown voltage >1000 V rms) from Logic Ground, AC Neutral, and the control input and output circuits.
Each channel of the Detector Unit shall function in accordance with the specific requirements of this standard and in addition shall operate without significant degradation with any sensor loop/lead-in combination which exhibits the following electrical properties as measured at the Detector Unit terminals of the lead-in:
Sensor loop and lead-in combinations used to verify the performance requirements of this standard shall consist of the following combinations of 1.828 m x 1.828 m (6 ft. x 6 ft) three-turn loops and shielded lead-in cable as illustrated in Figure 6-6.
Detector Units shall detect all vehicles which ordinarily traverse the public streets and highways and which are comprised of sufficient conductive material suitably located to permit recognition and response by the Detector System.
Vehicles are classified by this standard in accordance with the reduction in inductance resulting when they are centered in the single 1.828 m x 1.828 m (6 ft x 6 ft), three-turn-test loop with 30.48 m (100 ft) of lead-in.
These minimum reductions are as follows:
Figure 6-6 TEST LOOP CONFIGURATIONS
Construction–Loop dimension tolerances shall be +50.8 mm (2 in.). Connections shall be soldered and waterproofed. Loops shall be installed in a non-reinforced pavement and located at least 0.914 m (3 feet) from any conductive material. Lead-in cable shall be spooled. Loop leads shall exit at one corner of the loop structures. All loop corners shall be chamfered 0.305 m (12 in.).
Loop Wire–Each loop shall be three turns of AWG #14 cross-linked polyethylene insulated, stranded copper wire, such as IMSA (International Municipal Signal Association) Specification 51-3, 1984, or equivalent. Loop inductance shall be between 60–80 microhenrys.
Lead-in Wire–The lead-in wire shall be AWG #14 twisted pair, aluminum polyester shield, polyethylene insulation, polyethylene jacket, inductance between 20 uH and 24 uH per 30.48 m (100 ft), such as IMSA Specification 50-2, 1984, or equivalent. For standardized test purposes, the shield shall be insulated from ground.
Field installation practices or Detector Unit design may require grounding the shield of the loop lead-in cable. Such grounding should be in accordance with the Detector Unit manufacturer’s recommendation. (Authorized Engineering Information).
Sawslot–The conductors shall be placed at the bottom of a 38.1 mm + 6.35 mm (1-1/2" +1/4 in.) deep by 6.35 mm (1/4 in.) wide sawslot. Pavement sawslot shall be filled with a suitable polyurethane or equivalent sealant.
The Detector Unit shall be capable of detecting any of the vehicles defined in 184.108.40.206 on any of the test loops defined in 220.127.116.11.
When detecting test vehicles as described in 18.104.22.168 and operating on any of the test loop configurations described in 22.214.171.124, each channel of the Detector Unit shall include means to adjust the sensitivity such that it shall not produce an output when the nearest point of any test vehicle of 126.96.36.199 is 0.914 m (36 in.) or more outside the loop(s) perimeter. A minimum of three sensitivity selections shall be provided for each detection channel.
The Detector Unit shall detect any vehicle described in 188.8.131.52 over any of the single loops described in 184.108.40.206 traveling within the speed range of 8.045 km to 128.72 km (5 to 80 miles) per hour.
The Detector Unit shall detect any vehicle described in 220.127.116.11 over all of the loops of the four loop configurations described in 18.104.22.168 traveling within the speed range of 8.045 km to 64.36 km (5 to 40 miles) per hour.
All channels of a multichannel Detector Unit shall be operating at the same sensitivity and connected to equivalent inductances for the purpose of these tests.
Each Detector Unit channel shall be capable of functioning in the following two front panel selectable modes:
When a Class 2 vehicle defined in 22.214.171.124, or larger vehicle occupies the center of any test loops described in 126.96.36.199, the Detector Unit shall be capable of maintaining a detection output for a minimum of 3 minutes.
A detection output between 100 and 150 milliseconds shall be initiated when a vehicle enters the sensor loop zone of detection.
If this vehicle remains in the zone of detection, the Detector Unit shall become responsive within a maximum of 3 seconds to additional test vehicles entering the zone of detection. The Detector Unit shall produce one and only one output pulse for a test vehicle traveling at 16.09 km (10 miles) per hour across the zone of detection of the single sensor loops defined in 188.8.131.52.
When operating in the presence mode, and following an occupancy of any duration, the Detector Unit shall recover to normal operation with at least 90 percent of its selected sensitivity within five seconds after the zone of detection is vacated.
When operating in the presence mode, the Detector Unit shall be capable of being set to produce an output in response to a step decrease in inductance equivalent to the minimum decrease from a class one vehicle as defined in 184.108.40.206 within not more than 100 milliseconds when tested on either of the single loop test configurations described in 220.127.116.11. In response to step return to the original inductance, the Detector Unit shall terminate its output within no more than 100 milliseconds.
18.104.22.168.1 Variation in Response Time
The difference between the minimum measured response time and the maximum measured response time for input changes in either direction, over any number of tests, to an input change equivalent to a Class 1 vehicle shall not exceed 10 milliseconds per channel multiplied by the number of active channels. The Detector Unit must be set to the proper sensitivity to detect a Class 1 vehicle.
The difference between the minimum measured response time and the maximum measured response time for input changes in either direction, over any number of tests, to an input change equivalent to a Class 3 vehicle shall not exceed 5 milliseconds per channel multiplied by the number of active channels. The Detector Unit must be set to the proper sensitivity to detect a Class 3 vehicle.
All channels of a multichannel Detector Unit which are ON shall be operating at the same sensitivity and connected to equivalent inductances for the purpose of these tests.
For certain specific surveillance applications involving vehicle speeds in excess of 72.405 km (45 miles) per hour, a more precise response time will be required. (Authorized Engineering Information.)
Each Detector Unit channel shall include means for accommodating the range of sensor loop/lead-in inductance.
The unit shall tune automatically upon the application of power. It shall operate with at least its minimum sensitivity within 2 seconds after application of power, and at 90 percent of its selected sensitivity within 5 seconds after application of power.
The Detector Unit shall automatically accommodate those after-tuning changes in the loop/lead-in electrical characteristics as might reasonably be expected to occur in undamaged loops, properly installed in sound pavement and exhibiting the electrical properties outlined in 22.214.171.124, without producing a false output or change in sensitivity.
After any reset, Reset Unit or Reset Channel, the Detector Unit shall operate with at least its minimum sensitivity within 2 seconds after the removal of the reset condition, and at 90 percent of its selected sensitivity within 5 seconds after the removal of the reset condition.
Each Detector Unit channel shall include means to prevent that channel from adversely interacting with any other channel. The means to prevent such interaction shall be either inherent, automatic, or manual switch.
Each channel of a unit with delay/extension shall have at least three modes of operation–delay, extension, and normal (neither delay nor extension). Channels 1 and 2 of four-channel Detector Units shall be the channels to include the delay/extension feature. Delay and extension timing shall be setable on a per channel basis with the timing programmed independently.
When selected, the output is delayed for the time set. If the vehicle departs before the time set, an output does not occur and the timer is reset. If a vehicle is present and the delay timer is active, when the delay inhibit is applied, the output shall become active. See Figure 6-7. This delay timing is controlled by the Delay/Extension input defined in 126.96.36.199.7.
The delay time shall be adjustable over the range from 0 to 30 seconds. The setability shall be within one second in the 0 to 15 second range and within two seconds in the 16 to 30 second range. The accuracy shall be + 1/2 second or + 5 percent of the setting, whichever is greater. When the Delay/Extension input is active, the delay shall be zero (0 to 0.1 second).
When selected, the output is extended after the vehicle departs the zone of detection for the time set. If a new vehicle arrives before the extension timer times out, the timer is reset, the output is maintained, and the timer resumes timing when the vehicle departs. See Figure 6-8. This extension timing is controlled by the Delay/Extension input defined in 188.8.131.52.7.
The extension time shall be adjustable in the range from 0 to 7-1/2 seconds. The setability shall be within 1/2 second. The accuracy shall be + 1/2 second. When the Delay/Extension input is inactive, the extension shall be zero (0 to 0.1 second).
All controls and indicators necessary for the operation of the Detector Unit shall be located on the front panel of the unit except as noted below. Multiple functions combined in a single control shall be permitted. The controls and indicators shall include, but are not limited to:
184.108.40.206.1 Solid State Channel Detection Outputs
The output interface of each channel shall be an independent, isolated, solidstate output. Each output device shall have the following characteristics:
220.127.116.11.2 Channel Status Outputs
Each Detector Unit channel shall provide a channel status output. The channel status output shall be a solid state device with the following characteristics:
18.104.22.168.3 Channel Status Reporting
The Channel Status Output shall provide for the communication of eight distinct status states as defined below:
Pulse width modulation shall be utilized to encode the eight possible states as described below:
The tolerance for all times listed above shall be + 10 milliseconds; the On time between pulses shall be 50 milliseconds + 10 milliseconds.
The Channel Status Output shall reflect the current fault status of the channel (i.e., the fault status shall be self clearing in the event that a fault condition clears).
The Channel Status Output shall maintain an output state, other than a condition generated during a Reset, for a minimum of 5 seconds. The Channel Detection Output shall maintain the conducting state during a fault condition only while the fault condition exists.
The Channel Status Output shall be in State 2 during RESET. Once the RESET is complete and the Detector Unit resumes normal operation, the channel status output shall return to State 1.
The Channel Status Output shall be in State 2 for channels that are disabled (OFF). The Channel Detection Output shall maintain the non-conductive state (State 2) for channels that are disabled.
The last channel failure status shall be stored in memory for future reference. Enunciation of the last failure status shall be accomplished through the use of the front panel indicators. If power is removed or the Reset is activated, the last channel status information shall be cleared.
The particular method employed to enunciate past failure status is not specified and will be manufacturer specific. (Authorized Engineering Information.)
22.214.171.124.4 Data Transmit Output (TX)
This output shall have 3 states: Mark, Space, and High Impedance. The output shall be in the High Impedance state except when transmitting to the BIU. The transmitter output shall go from the High Impedance state to the Mark state until the first Start Bit is sent. The Transition Region shall be defined as any voltage between a Mark and a Space.
126.96.36.199.4.1 Mark State (Binary 1)
During Mark, the TX output shall be less than 0.5 VDC when sinking 4 milliamperes current.
188.8.131.52.4.2 Space State (Binary 0)
During Space, the TX output shall be greater than 3.5 VDC when sourcing 4 milliamperes current.
184.108.40.206.4.3 High Impedance State
The TX output shall have an impedance greater that 1 Megohm in the High Impedance state. When connected to the following loads, the TX output in the High Impedance state:
220.127.116.11.4.4 Output Impedance During Power Off
When power is OFF, the output impedance shall be greater that 300 ohms when measured with an applied voltage not greater than 2 volts in magnitude to circuit common.
18.104.22.168.4.5 TX Output Shorts
The TX output shall not be damaged under these situations:
22.214.171.124.4.6 Rise/Fall Time
The transition time from the Space to the Mark voltage or from the Mark to the Space voltage shall be less than 2.5 microseconds or 4% of a bit time, whichever is less. This shall apply with 3750 picofarads attached to the TX output. There shall be no reversal of the direction of voltage change while the signal is in the Transition Region. The Transition Region shall not be reentered until the next change of signal condition.
126.96.36.199.4.7 Transient Withstand
The TX output shall not be damaged by application of the transients described in 188.8.131.52 through 184.108.40.206
The protocol for this port is under definition.
Inductive Loop Detector Unit types AC, BC, CC, and DC have this communication port.
220.127.116.11.1 Communication Port Electrical Requirements
This port, RX and TX and DC Common, is an unbalanced, +5 volt nominal, standard NRZ (Mark/Space) format, asynchronous serial communication port. For compatibility with systems currently in use, when TX is shorted to the Ch 2(+) Output and when RX is shorted to the Ch 4(+) Output, TX and RX must not interfere with Ch 2(+) or Ch 4(+) operation. See 18.104.22.168 for RX specification details and 22.214.171.124.4 for TX specification details.
126.96.36.199.2 Baud Rate
The port shall be capable of operation at a baud rate of 9600 bps ±1%. The width of 1 bit shall be the reciprocal of the baud rate.
188.8.131.52.3 Communication Parameters
The standard NRZ (Mark/Space) format shall be used. Further specifications are under definition.
184.108.40.206.4 Slot Addresses
The address of a Detector Unit slot is "hard-wired" at each Detector Rack connector. A logic 1 shall be created by wiring an address pin to DC Common. Open or +24VDC shall be a logic 0. Slot 1 shall be Address 0 and Slot 15 shall be Address 14.
220.127.116.11.1 Connector Description
Two and four channel card rack units shall mate with a 44 terminal, double row, 3.2 mm (0.156 in.) contact spacing, Cinch Jones card edge connection 50-44A- 30M, or equivalent.
18.104.22.168.2 Connector Terminations
Input / Output connector pin terminations shall be as shown in Table 6-2.
|A||Logic Ground||1||Channel 1 Delay/Extension Input|
|B||Detector Unit DC Supply||2||Channel 2 Delay/Extension Input|
|C||External Reset||3||Detector Unit Address Bit #3|
|D||Channel 1 Loop Input||4||Channel 1 Redundant Loop Input (Optional)|
|E||Channel 1 Loop Input||5||Channel 1 Redundant Loop Input (Optional)|
|F||Channel 1 Output (+)||6||Detector Unit Address Bit #0|
|H||Channel 1 Output (-)||7||Channel 1 Status Output|
|J||Channel 2 Loop Input||8||Channel 2 Redundant Loop Input (Optional)|
|K||Channel 2 Loop Input||9||Channel 2 Redundant Loop Input (Optional)|
|L||Chassis Ground||10||Detector Unit Address Bit #1|
|M||Reserved (AC Neutral)||11||Reserved (AC Neutral)|
|N||Reserved (AC Line)||12||Reserved (AC Line)|
|P||Channel 3 Loop Input||13||Channel 3 Redundant Loop Input (Optional)|
|R||Channel 3 Loop Input||14||Channel 3 Redundant Loop Input (Optional)|
|S||Channel 3 Output (+)||15||Detector Unit Address Bit #2|
|T||Channel 3 Output (-)||16||Channel 3 Status Output|
|U||Channel 4 Loop Input||17||Channel 4 Redundant Loop Input (Optional)|
|V||Channel 4 Loop Input||18||Channel 4 Redundant Loop Input (Optional)|
|W||Channel 2 Output (+)||19||Data Transmit Output (TX)|
|X||Channel 2 Output (-)||20||Channel 2 Status Output|
|Y||Channel 4 Output (+)||21||Data Receive Input (RX)|
|Z||Channel 4 Output (-)||22||Channel 4 Status Output|
22.214.171.124.3 Type A Two Channel Without Delay / Extension Timing
The following pins shall be inactive: P, R, S, T, U, V, Y, Z, 1, 2, 13, 14, 16, 17, 18, and 22.
126.96.36.199.4 Type B Four Channel Without Delay / Extension Timing
The following pins shall be inactive: 1 and 2.
188.8.131.52.4 Type C Two Channel With Delay / Extension Timing
The following pins shall be inactive: P, R, S, T, U, V, Y, Z, 13, 14, 16, 17, 18, and 22.
Pin 1 through 22 is on the top (component) side and pin A through Z is on the back (solder side). Polarization keys shall be located at three positions:
Between B/2 and C/3
Between M/11 and N/12
Between E/5 and F/6
Pins 3, 6, 10, and 15 are address pins for Type AC, BC, CC and DC Inductive Loop Detector Units. When one of these Detector Unit types are installed, it will be assigned an address associated with the Detector Unit position in the Detector Rack.
Pins 19 and 21 are the TX output and RX input for communication with the Detector Unit. The communication protocol is under definition. (Authorized Engineering Information.)
Previous | Table of Contents | Next
Keywords: Traffic detectors, sensors, detector installation, detector maintenance, signalized intersections, intersection safety, intersection treatments, infrared sensor, inductive loop, magnetometer, video image processor, microwave radar sensor, laser radar sensor, acoustic sensor, ultrasonic sensor, magnetic sensor