This is a very simple circuit that can indicate the last action taken on a Momentary Switch. An example of this is if you are using a momentary toggle switch to control the points on a Model Rail Layout. This circuit will latch on an Indicator when the switch is used, that indicator will remain ON when the switch returns to the centre OFF position. When the switch is used in the down momentary position the first indicator will switch OFF and the second Indicator will switch ON, and remain like that even when the switch returns to the centre OFF position.
Now voltages:  The circuit is capable of accepting a range of voltages.
Coil 1 – C1 = 9v to 16v ACDC,
Coil 2 – C2 = 9v to 16v ACDC,
The Relay contacts will handle 2 Amps upto 30vDC ( A suggestion fix the circuit board near the points it is controlling, then run a 6 core cable back to the Control Panel for Indicators and the toggle switch, this assumes you have a 0v (Black) Bus Bar.)
Under no circumstances run a CDU through the relay contacts, the relay will fail.
Equivalent to the Gaugemaster Universal Relay Switch GM-500
A few of its applications:
Points Indicator.                                               Points, Signal Control.
Home & Distant Signal Control                       Control Panel Display
Automatic Points Switch                                 Automatic Shuttle Control
Station Stop Manual Start                               Running Lights
Siding Occupied Indication                             Train Blocking
Common Rail Control                                       Electro Frog Points
Isolation of Track                                              Reversing Loop Control
Reversing Figure 8 Control                              Siding Isolation
Automatic Reversing  
Replaces the function of a Peco PL15 twin micro switch 
To name a few:...