Original page created on 10/07/2012.
The manual control will be done by a simple switch, for the reason indicated above: it only requires one input per turnout, instead of two in the case of a push-button control.
There is, however, one disadvantage, namely that the handle of the switch remains in position, even if the turnout position changes under the effect of a route control. Hence, the need for LEDs which indicate the actual position of the turnouts by feedback.
The problem of the possible contradiction between automatic control and manual switches position arises, as mentioned above, with the switch control system (as opposed to the momentary push-buttons). If the switch remains closed, which means turnout diverging, the automatic route control must be able to return the turnout to the direct position.
It is therefore necessary to transform the permanent control (the contact remains closed) into pulse control. This is called edge control, up or down. On the programmable module, this is achieved by a timing function (B type: passing, activating control for a rising edge, i.e. when the contact closes, or passing, de-activating control for a falling edge, i.e. when the contact opens). A very short time is set for the output pulse, for example 10 ms, so that there is no chance that an automatic (route) control and a manual control will happen at the same time.