SSM-6LE & 12LE Monitor FAQs

General Overview

The SSM-LE series Signal Monitors exceed all the requirements set forth in the NEMA Standard TS-1-1994, Part 6. These units are intended to provide enhanced conflict and voltage monitoring for traffic controller assemblies with additional capabilities for broader fault coverage and diagnostic troubleshooting. The SSM-6LE and SSM-12LE units include a Full Intersection Liquid Crystal display (LCD) along with an communications port which is used to communicate with a Personal Computer using EDI ECcom software. Monitor status, event logs, and Signal Sequence History logs are stored in nonvolatile memory for diagnostic and archival purposes. Two modes of Flashing Yellow Arrow PPLT support are provided.


When the appropriate Flashing Yellow Arrow (FYA) channels are selected, does the monitor ignore the unused yellows on channels 1,3,5, and 7?

The unused yellow and red inputs of the protected channel pair are not ignored by the monitor. This means that a dummy load resistor needs to be on the yellow output to prevent a conflict. An unloaded load switch output will be detected by a NEMA monitor as it is active all of the time. Likewise with the red signal, but having the red sensed active does not generally cause an issue.

The reason that the SSM-12LEC  does not blank out these signals is that there may be cases where signals are in fact driven by these yellow and reds. The CU drives the RYG of this protected channel (1,3,5,7) as if it were a three section signal even though the red and yellow are not driving lamps. So if for example, the cabinet is fully loaded with 8-phases plus 4 FYAs, then all channels are used. If an additional right turn overlap is needed, then a user could drive the right turn overlap from the corresponding protected channel and the right turn arrows become the loads. In that case a user would turn on the SSM switch for that channel, and the monitor would detect malfunctions of Dual Indication and Clearance and Red Fail.

The SSM-12LEC was updated with FYA capability before the NEMA TS2 FYA Standard was developed and is limited by DIP switch programming. It would be my recommendation to always use the MMU2-16LE SmartMonitor when an intersection is driving FYAs. The MMU2-16LE SmartMonitor will operate in the NEMA TS1 mode, but it has more FYA capability than the SSM-12LEC. To answer the question that you asked, the MMU2-16LE has programming to configure it to ignore the unused red and yellows of the protected channel pair (FYA Enable Red / Yellow). Thus the dummy load resistors are not needed. Other features such as flash rate detect, yellow trap detect, and dynamic conflict clearance monitoring also come with the MMU2-16LE SmartMonitor.


What is the difference between a SSM-12LEC and a SSM-12LE?

The SSM-12LEC was a product derived from the SSM-12LE standard product. In the “early days” before Ethernet in traffic cabinets there was a desire to get the monitor log data remotely back to a TMC or Signal shop. Back in the 1990’s EDI worked with Eagle (now Siemens) to incorporate an Eagle protocol into the SSM-LE series firmware. This allowed the SSM-LEC to transfer a simple fault log back to the EPAC controller and then relay it through their system (Marc, Actra, Tactics, etc.) to central. It also synchronized the monitor real time clock to the controller clock so that the time and date of the monitor reflected the correct time in the controller.

So the difference is only in the firmware installed in the monitor. If the serial cable is not connected between the SSM-12LEC and an EPAC controller then the monitors work identically.

Normally what you are looking for is provided by the system software such as Tactics or Centracs. They typically assign a hyperlink for each cabinet to launch ECcom and pass it the IP address of the MMU. In this case the system software maintains all of the IP addresses for anybody on the network. For an agency without such system level software there are two approaches:

  1. The ECcom Search function will send out a UDP datagram asking all EDI monitors to respond. A table will be created to show the responses and then you select one.
    • The Search function is not designed for this purpose however, it may or may not work for your solution. First, many networks are set to block UDP Broadcast messages. If that is your case, end of discussion. Second, the responses to the broadcast message will arrive all at the same time or close. Thus not all will be received by the PC because of Ethernet collisions. No retries are provided, it is UDP. You can try it but depending on the configuration of the network and how many monitors are installed, I don’t think it will fulfill your needs.
  2. Set up a collection of shortcuts to launch ECcom onto your desktop or in a folder. Each shortcut will be named with the associated cabinet and will launch the ECcom software with a command line option that has the IP address of that installed MMU.
    • See section 3.2.2.1 (Ethernet) for the command line option format. This method is static in that any change to a MMU’s IP address in the field must be accompanied by a change to the related short cut on your PC or the Server PC.

We recommended to Sensys that they add Message 0 interface to their setup options.  This SDLC capability would allow gathering of state change data directly from the controller.  For example, Econolite’s Autoscope detectors listen to this Message 0.  Message 0 is standard in a TS2 cabinet with an MMU, but several controller manufacturers and software vendors also support Message 0 in TEES and TS1 cabinets. 

If the CU can transmit the Type 0 message without expecting a response from the MMU then it would work for TS1 and 332 cabinets that will not have an MMU installed.


Is there an MMU with an IP interface?  Is the protocol the same as the 2010-ECLip?

Yes, it is the MMU-16LEip.


For a TS1 cabinet with a CMU, Sensys recommended that we change the CMU to an EDI MMU2-16LIip and connect an SDLC ‘Y’ cable to the controller – essentially converting the TS1 cabinet to a TS2 cabinet. This may work in a 16 channel TS1 cabinet, but Sacramento did not have this cabinet option to test.

There are several options for TS-1:

  1. If the CU and Sensys support the Type 0 message without an MMU installed, then the cable works.
  2. The MMU2-16LE SmartMonitor can operate in the Type 12 with SDLC mode. This makes the CU think it is connected to a 16 channel MMU but the interface to the technician is still 12 channels of RYGW. It requires the Ped Walks to be monitored on channels 2W, 4W, 6W, and 8W. It does not require a 16 channel cabinet.
  3. Use the MMU2-16LEip Type 16 mode and rewire the Peds to channels 13-16 (or 9-12) R and G on the MMU.

We got this to work by landing pin MMU-hh to Logic Ground (I tried letting it float and landing to 24VDC). On the MMU2-16LIip, I set the Type 12 switch in Options. However, the reds from 13-16 tied up to 120VAC showed as conflict with Peds on 9-12. (I tested Sensys successfully by disabling the Ped movements.) On the MMU2-16LIip, I set the Walk switch in Options and the cabinet cycled successfully with Ped movements. However, we are concerned about the safety role of the monitor in this configuration.

Pin HH (Type Select) is floating in the 12 channel mode and connected to Logic Ground to force Type 16 mode in the MMU. Alternately you can set the Force Type 16 option in the MMU2-16LE and it will monitor 16 channels of RYG. The Ped inputs will likely need to be remapped as the Walk inputs of TS-1 are not provided in the Type 16 mode.


I don’t know what you mean by “the reds from 13-16 tied up to 120VAC showed as conflict with Peds on 9-12”. I also don’t know what the “Walk switch in Options” means.

We should discuss in more detail how to accommodate Peds in this mode. Peds are not safely monitored in the TS-1 mode, since the DW inputs are not monitored. In a TS-2 MMU, both the Ped DW and Ped Y can be monitored to detect a failure of the DW signal and a Conflict during flashing DW. TS-2 is far safer than TS-1 in that regard.


To fully convert the TS1 cabinet to TS2 with the MMU, I believe that I also have to provide Ped Don’t Walk signals to the MMU (ch 13-16). This is additional wiring change to the MMU connector. Though not an Econolite cabinet, Econolite may have an adaptor cable for the MMU. Do you see any other options for the TS1 cabinet?

The MMU2-16LE SmartMonitor can operate in the Type 12 with SDLC mode. This makes the CU think it is connected to a 16 channel MMU but the interface to the technician is still 12 channels of RYG. It requires the Ped Walks to be monitored on channels 2W, 4W, 6W, and 8W. It does not require a 16 channel cabinet. Use the Type 16 mode and rewire the Peds to channels 13-16 (or 9-12) R and G on the MMU.


What is the protocol for the EDI MMU2-16LIip IP interface?

At this time the MMU2-16LEip and SSM-12LEip do not provide the PATH message datagram. Use the SDLC bus as described earlier.

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