Some control gear units for light sources, e.g. fluorescent lamps or LEDs, feature a push-dim interface (see footnote). This is the simplest type of lighting interface. Here, the phase of the control gear mains connection is additionally connected to a push-button at its control input. A short press of the push-button means on/off, holding the push-button means dimming up/down.
One significant advantage in comparison to the 1...10-V interface is that it only requires two wires inside the wall. In existing lighting installations with mere switching capacity, this is mostly the situation at hand. Only one additional wire in the ceiling is required for the permanently applied phase (see figure), which can be achieved with little effort in many cases. It is possible to connect several push-buttons in parallel to provide several operating panels. Manufacturers’ installation information must be observed.
This solution should only be used for the operation of individual control gear units. For instance, when operating two control gear units via push-dim, it is possible that a very short push-button press only reaches the interface threshold value for one control gear unit and triggers switching. The other control gear unit does not switch, since the threshold value (due to device tolerances or installation conditions) was not reached. Now, the units are in different switching states. At the next push-button press, both units are switched. The inactive one is switched on, and vice versa. Afterwards, both control gear units are once again in different switching states. The greater the number of control gear units, the more likely the occurrence of asynchronisms of this type becomes.
If several luminaires are to be operated with the push-dim functionality, then e.g. control units of light management systems can be used that have a push-dim interface at the input, but control the lights on the output side with DALI (see below, figure).
Term used by control gear manufacturer BAG electronics for operating a control gear unit with a push phase. Terms as well as functions (in detail) vary between manufacturers, e.g. "TouchDim" is used by OSRAM while Philips uses "Touch-&-Dim".