.... and as DavidCBroad indicates (I believe) you need to set up a sequence of moves.
I've used David's drawing as a basis for the following diagrams.
First, my two Barry slips are in a fiddle yard, and the 'kick back' turnout in the Barry slip is to enable me to have all the pointwork at one end of the fiddle yard on a 4 foot long board. There is more or less the same pointwork on another 4ft board at the other end of the fiddle yard.
A is the origin of trains (my down line) travelling to the loop B - C.
D is the kick-back / deadend siding (used to store a 'railmotor').
A sequence is thus train from 'A' travels to either 'B' or 'C' siding (loop) and for operational purposes I have decided that 'C ' is the loop line that will kick back into 'D'.
I'm using 12v AC to control the point motors, there are 28 of them in the fiddle yard, and by using the AC there's just the 0v as a common 'Busbar' to one contact on the point motor, and one -15v / +15v wire from the control panel switches to the other contact
Using the Fulgurex point motor, there are two sets of changover switches available, one is used for the crossing 'V', the other is now used to 'control' the other point motor.
By simple experiment e.g. "Does it work?", it became clear the 0v is the one to 'control' which point motor works.
'Z' = 0v. The other contact on that changeover switch is not connected to anything.
These three rough diagrams hopefully explain how each point motor can only be operated in set circumstances,
I'm using common return for the track feeds.
It's fun working on the underside of the baseboard, trying to get this right for the top