Relay logic - Controlled siding absolute signal

This is an example of the relay logic used to operate a railroad wayside signal at a control point with a diverging route that does not use signals, especially in the instance of a controlled siding. The toggle switches act as control signals coming from the dispatcher desk. Each toggle simulates block authorization which gives the signal the appropriate aspect. Aspects available are Stop, (red/red) Restricting or Diverging Restricting, (red/lunar) Approach, (yellow/red) Advance Approach (yellow/yellow) and Clear. (green/red) The purpose for this circuit is to demonstrate the relay logic more than the actual function of the signal. I apologize for the crudeness of the circuit as I only have SPDT relays and wavelength-specific LEDs in the software. Therefore several coils are tied together to create the DPDT relays needed. For Lunar white, I substituted with a light blue or indigo colored LED. Actual track circuits look nothing like this however the relay logic used here is very similar to what a signal would look like before the industry moved towards solid state. Explanation of switches: (Left to Right) 1 - 1st Block authorization. Coming from the dispatcher and allowed through electronic interlocking the first block switch will close to actuate the first series of relays and line up the signal. 2 - switch position. The turnout switch at the junction will either be lined for a main line movement or into a divergence. If there is an error the interlocking will not open. Otherwise when this switch is closed it will actuate the series of relays to put up a display for main line movement. If the switch is open when the 1st block is authorized it will put up a display for the diverging route. 3 - 2nd block main route authorization. When the switch is closed it will line up the signal to show an aspect for the second block. 4 - 3rd block main route authorization. When the switch is closed it will line up the signal to show an aspect for the third block. In most situations a 3-block system is used to express an all-clear. Anything less than a "clear" signal will be expressed with 2 or less blocks. When this switch is closed it will line up the signal to show an all clear on the main line.

published 9 years ago