The watchdog signal is sent for 5 seconds whenever voltage changes from 0 to any other value at the output a TIU channel.
So I'm curious. Has anyone tried using a double pole single throw switch such that the common is connected to the transformer, the other poles connect to TIU hot input 2 and 3, and the TIU 2 and 3 hot outputs are connected together, and then to the track? Except for voltage spikes when toggling the switch (perhaps a TVS would stop that?), it should generate the watchdog whenever the switch is toggled. Any running engines should continue running since the power isn't really interrupted.
I just reread Barry's comment above again. So instead of having the DPST switch on the TIU inputs, have it on the outputs. Anyone try that?
Eric