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slowly, until a small push on the door will open it.
No electric circuit is opened or closed. A few seconds
after the hand is removed the current is decreased,
once again reducing the pull of the magnet and locking
the door.
Ringing a bell: Sometimes a locked door is opened
from the inside by a guard who must be alerted by
ringing a bell or talking through an intercom. The
button normally used to ring a bell will be replaced
by a change-sensor. Putting a hand close to the
sensor will cause the current to gradually increase in
a buzzer or LED display, alerting the guard. In this
technique, no electric circuit is opened or closed.
When the hand is removed, the current gradually decreases
and the buzz or the LED light at the guard’s
station returns to its initial very weak state.
keeps the door pressed tight to the doorpost,
exerting a force of hundreds of kilograms. The
button that is normally used to leave the installation
is replaced by a change-sensor. When a hand
comes close to the control box, the current passing
through the electromagnet will be gradually reduced
so that a light push on the door will open it.
In this way, there is no electric circuit that is created
or broken (and the pull of the magnet continues all
the time). A few seconds after the hand is removed
from the control box, the current is increased and
the magnet returns to full strength.
Electronic lock: The electronic locks have a built-
the door remains locked. Pressing a switch closes a
circuit and sends a current through the magnet, releasing
the tongue of the lock. In this case, the usual
button will be replaced by a change-sensor. Putting
the hand near the control box or touching it causes
the electric current in the electromagnet to increase
Hospitals
Aside from the security sphere, Machon Zomet’s
Jerusalem’s Shaarei Zedek Medical Center near Bayit
Marans, Rozen, and their team of frum engineers.
One of the more interesting devices sold by the
institute is the “Shab-et,” a pen used by many Israeli
doctors. While writing is a biblical prohibition,
temporary writing that fades after several days
is only banned rabbinically. By making pens whose
ink gradually disappears over the course of several
days, Zomet has allowed doctors to keep records on
Shabbos that can be transcribed or photocopied after
Havdalah.
Explains Zomet: “The Shab-et is in regular use in
many hospitals, by security forces, and even in the
if necessary). The use of a Shabbos pen is permitted
only if the action is so essential that it takes precedence
over the rabbinical prohibition of writing using
temporary ink.”
Another innovation introduced by Marans,
Rozen, and team is the food cart grama plug. It is
generally accepted that it is very important for patients
to be served hot food. It is true that not all
patients in a hospital are considered to be in mortal