Q: I am setting up a yard control panel with a CML Electronics DTM30. For the DTM30 to know what state a turnout is in, it can issue an interrogate command but my DS54's do not seem to respond with this information. Is there a trick to this?
A: According to CML: The DTM30 makes use of the “Interrogate” feature that all modern Digitrax systems use.
After power up, the Command station normally sends out 8 switch commands.
All accessory devices respond to these, and send LocoNet messages back reporting sensor states and point states.
The DTM30 can also send this interrogate sequence, but normally this is not required since the command station sends this out after power on or after track power on.
The DS54 accessory decoders send up to 8 LocoNet messages when the interrogate sequence is issued.
These will be either Output State, Turnout Feedback or Sensor messages, depending on how the DS54 is programmed:
1. If its 8 inputs are programmed for sensors, then the DS54 will generate sensor messages
2. If 4 of its inputs are programmed for turnout position feedback – using switches on the turnout tiebars – then it will generate “turnout feedback” messages.
3. It will also generate “Output state” messages indicating what the state of the DS54 motor control outputs.
3a: If the DS54 is controlling a tortoise type motor, then these will indicate the turnout position in the absence of position feedback switches.
3b: If the DS54 is controlling solenoid type point motors, then this message is not generated correctly and will not indicate turnout position.
In the last case – solenoid motors, and no position feedback switch wiring – then the best approach is to use the “initialize” feature of the DTM30 to set all turnouts to a known initial state.