Some rule leniently about devices and appliances whose functioning is barely distinguishable from regular devices but whose inner workings have subtle differences so that the devices can be considered to work via “grama.” Three different methods are used: 1) removing an impediment (hasarat ha-mone’a); 2) activation by means of a scanner; 3) activation by extending the present state (Peninei Halakha: Shabbat 17:18).
In practice, it would seem that if one’s action causes a device to turn on within a short time, as it normally does, then even if the appliance has been programmed to turn on in a grama-like way, one may not turn it on. The internal workings of the machine do not concern us; if it turns on in a way that looks normal, then that is not considered grama. Therefore, elevators and automatic doors may not be turned on via grama; since the goal is for them to function in the normal way soon after being turned on, it is not considered grama. Similarly, one may not travel using an electrical wheelchair or golf cart on Shabbat, even one that is specially designed for Shabbat use (such as a “kalno’it”), since it nevertheless operates in the way that one would operate a similar device during the week.
In contrast, if one’s action causes a device to turn on with a significant delay, and the device is designed with one of the three methods listed above – turning it on is considered grama. Such a device may be used when urgently needed on Shabbat, and when necessary on Yom Tov. These principles apply to arming a security system as well. If turning a key will cause the system to work via grama, and it will not actually arm itself until about five minutes later, that is considered grama, and may be done in a case of great need.
These laws are the same on Shabbat and Yom Tov. Therefore, one may not enter a room where an electrical mechanism turns the lights or air conditioning on automatically when someone enters. Likewise, if exiting the room will cause the lights or air conditioning to turn off, it is forbidden to leave. Turning the electricity or air conditioning on and off in this way is not considered grama. Rather, it is akin to turning appliances on and off with a remote control, which is the normal way to turn them on and off. It is irrelevant whether the normal way involves pressing a button or entering and exiting the room. (See Peninei Halakha: Shabbat 17:12 regarding a case of pressing need.)