Trafictec CMU Conflict Monitor Unit

Monitors selected traffic controller channels for conflicts.


The Trafictec CMU Conflict Monitor Unit, which is optional for use with the SBC-2400 Traffic Control System, monitors selected traffic signal controller channels for conflicts. There are 8 input lines and 6 CMU channels. Two sets of input lines are tied together, forming a single signal group (i.e., Green and Walk) that can be monitored as one channel. When two channels are in conflict, the CMU will activate a conflict signal. This signal is read by the traffic controller, which will then place the intersection in flash. The conflict signal is latched and can only be cleared by a manual reset. The latching relay maintains the fault status during a power outage.

Front panel LEDs illuminate when a channel is active. A small super capacitor is used to power the LED latch and will maintain the information for about 2 hours. After this period, the front panel LEDs may not show the correct information, but the latching relay will stay in the fault state until manually reset.

The CMU channel inputs can be one of three types (12 VDC, 110 VAC or 220 VAC) and must be selected at the time of order. The CMU is powered by a 12 VDC power supply in the traffic cabinet.

Conflict Monitor Unit

Clean, Single-Board Design

All channel inputs and power enter the CMU via a front panel DB15P connector. The +12 VDC power passes through a diode, and a 100 µF capacitor acts as an input filter. All circuitry, including the supercap recharging circuit, is powered by 12 VDC. There are no other power supplies in the CMU.

The channel inputs pass through a pre-selected resistor based on the signal voltage. The signal then drives an opto-isolator and then back to the channel return pin. The output side of the opto-isolator is pulled up by a 47 kohm resistor. When the input is On, the output is driven low to ground.

The channel signal then enters a NOR gate matrix, where each CMU input channel is OR’ed with the other input channels. Both inputs being low will invert the output signal and cause the high state to enter a series of DIP switches. These are used to select which channels are monitored for conflicts. The user turns on each switch to select pairs of input channels which should never be both on at the same time, or a conflict will be detected. There are 15 DIP switches in two banks of 8. The last switch is not used.

Two conflict signal branching circuits are at the exit of the DIP switches:


Circuit one is the front panel LED latch. The conflict status of the channels is shown by LEDs on the front panel, and this information is latched following a conflict so the technician can see what channels caused the fault. The LED latch driver has a small super capacitor to save data for about 2 hours. If the power is interrupted for a longer period, the LED data may not be valid.


Circuit two is the conflict signal, which is branched to the delay timer/ latching relay driver. Because a slight residual voltage may exist on the channel input after the controller turns off the signal output, a 450 ms delay allows all CMU channels to stabilize and not give false conflicts. If the conflict is present for longer than this delay, the latching relay is driven active and can only be reset by a manual pushbutton on the CMU front panel.

Product Specs

Operating temperature -20°C to +75°C
 Input power +12 VDC at 100 mA max
 Conflict delay time 450 ms ± 50 ms
 CMU signal latching Latched
 CMU signal reset Manual
 Relay type Latching type with dry contacts
 Channel selection DIP switches
 Channel voltage 12 VDC, 110 VAC or 220 VAC (specified at time of order)
 Indicator 7 LEDs, six for channels 1-6 and one Fault LED.
 Isolation Optical couplers rated 5 kV
 Mating connector DB15S (female)

DB15P Input Connector Pin Assignments

 1 Channel 1 first LED
 9 Channel 1 first LED (electrically tied at opto coupler output to pin 1 circuit)
 2 Channel 2 second LED
 10 Channel 2 second LED (electrically tied at opto coupler output to pin 2 circuit)
 3 Channel 3 third LED
 11 Channel 4 fourth LED
 4 Channel 5 fifth LED
 12 Channel 6 sixth LED
 5 Input signal return (DC- or AC-)
 13 Not used
 6 Not used
14 Not used
7 Conflict signal output (Ground true)
15 +12 VDC power
8 Ground (+12 VDC return)

Dip Switch Matrix

Bank 1 Bank 2 
1 Channels 1 & 21 Channels 2 & 6
2 Channels 1 & 32 Channels 3 & 4
3 Channels 1 & 43 Channels 3 & 5
4 Channels 1 & 54 Channels 3 & 6
5 Channels 1 & 6 5 Channels 4 & 5
6 Channels 2 & 3 6 Channels 4 & 6
7 Channels 2 & 47 Channels 5 & 6
8 Channels 2 & 58 Not used