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About The SPC System

SPC Is a method of controlling the points of a model railway electrically using twin coil solenoid point motors. Traditionally these motors have required three wires to control them. One of the wires is a common return from the two coils and can be linked together with other common returns to reduce the number of individual wires. However, this still means each additional point needs two extra wires from the control panel to switch it. This soon mounts up and a smallish layout with 35 points requires a huge 71 wires from the control panel to the layout to work the points! With the SPC system 35 points require only 36 wires maximum. SPC achieves this saving by using energy differently to improve both the control and reliably of the point control system.

Special Track Formations

One of the great strengths of the SPC system is its ability to control more than one point motor on a single switch and with a single control wire to the layout. Apart from the obvious saving in wiring this allows complex track formations to be set from one switch, reducing mistakes and the inevitable derailments caused by them. A crossover track, a single slip, three way point or even the scissors crossover can all be set using one switch and in all these cases with only two control wires.(2)    

We have even ganged a single slip and two points together to form an entrance/ exit from a branch line or goods yard. The only one that has defeated us so far is the double slip, and for this we need two switches with the two control wires simply because it has four directional settings!

(2) In addition to the signal wire all SPC point motor control units require connecting to a "Common" wire which is daisy chained to all of them

SPC Point Motor Switching Units

The secret of the power and reliability of the SPC system is the point switching unit. Charged and controlled by the signal wire it stores the energy to throw the point actually at the point motor, releasing it on the command of the switch in the control panel. Because the command is the change of polarity fed to the switching unit, multiple point switching units can be commanded to change at the same time with the same reliability as a single unit. The retro fit SU 1 switching unit however does not have a point motor fitted as it is intended to operate other types of twin coil point motor such as the surface mounted motors or to be used to "retrofit" the SPC system to an existing three wire system.

We can supply a Seep point motor mounted on a SPC unit circuit board.

SPC Testing and Installing Tools

We produce two testing/installing tools; the TI 1 for fitting and testing SPC point motors and the PMTU 1 for testing non SPC point motors. The TI 1 is actually an SPC control panel with only one switch in a convenient hand held case and it emulates the full control panel in every way except working with multiple switches. The PMTU 1 is a complete SPC system in a hand held case; a control panel with one switch combined with a point switching unit. Both test tools allow the layout builder to operate the point motor they are installing before the layout is wired up or instead of the layout wiring for testing purposes.

SPC and DCC

systems can easily be upgraded to or built as DCC controlled systems with or without manual control of all or part of the layout. The stationary decoders for the points are simply placed in the control box and work via a selector switch to choose either DCC or manual control. The DCC controller can switch the points or they can be computer controlled via the DCC system but with the flick of a switch the fitted points are manual again. It is even possible to have a DCC and therefore computer controlled mainline and a non DCC goods yard or locomotive depot area and still have manual control of the DCC equipped mainline points!