With the increased awareness of the need for greater security precautions and with the steady advance of technology the use of closed circuit television is becoming more and more widespread. It is now used not only in areas protected for reasons of security but also in private homes and in many public institutions. Many systems have also been installed in Torah institutions and synagogues, both in Israel and abroad.
For example, the Old City of Jerusalem, including the Western Wall Plaza, is covered by hundreds of closed circuit cameras. This is also true of the Machpelah Cave in Chevron and many other sites.
This subject has been studied in depth by The Zomet Institute, and many articles analyzing the halachic aspects of these devices have been published. Here is a summary of the situation:
a. Many years ago (in 5742, 1982) The Zomet Institute turned to Rabbi Moshe Feinstein and received halachic approval for use of such equipment. Ten years later (in 5751), Rabbi N.Y. Neubert concurred with Rabbi Feinstein's opinion, and he later published an article in Techumin, volume 14 (5754). Rabbis living in Jerusalem from all sectors of Judaism agreed with the halachic approval given for cameras in the area of the Western Wall, including Shabbat control for metal detectors at the entrance gates, which operate on a similar principle. This was summarized in several articles in Techumin, volume 25.
b. The principle involved is based on a halachic ruling that if a device does not contain any electrical element of "fire" (such as a glowing filament or a heating element) there is no prohibition on Shabbat to cause a change of current level or a change of voltage, as long as no new electric circuit is formed. This accurately describes the situation in a single television camera.
c. Nowadays the standard equipment is more complicated, including several cameras broadcasting simultaneously onto a single screen. Image processing software continuously analyzes the pictures, and if human movement is detected the image on the screen is enlarged. In addition, the pictures are only saved if motion is detected and not all the time, as was done in the past.
d. As long as a person does not do any physical action with his hands or his body, and there is no physical sensor that is affected (such as breaking a light beam that shines on a photo-electric cell, a prohibited action), but all the action is internal to the computer software, no prohibition is being violated. And such equipment can be used even if there is no definite security need.
e. Storage of data as triggered by detected motion is only permitted for security or similar essential needs. If the purpose is to watch the pictures at a later time (such as is commonly done in weddings, etc), most rabbis prohibit the activity as an action of "giving the final touch in creating something" (makeh bapatish – literally, striking with a hammer), at least from the point of view of a rabbinical decree.
f. Thus, using closed circuit TV to record festive or important occasions on Shabbat is prohibited (and this includes the recording of Torah lessons).
For more information (in Hebrew):