21-12-2009, 08:22 PM
To prevent unauthorized or prolonged telephone conversations, a limiting device is attachable to an ordinary telephone set by means of a padlock means with removable key.A knob is provided for setting the timer which is enabled to rotate a rotatable part of the timer only after the knob has been depressed.The timer can be set only when one of the shut-off pushbuttons of the telephone set is depressed. The timer also operates to depress either pushbutton as the preset conversation time expires. The major disadvantage is that it is not possible to reset the timer or retard the movement of the timer in order to prolong the conversation time, because this may result in one of the pushbuttons being pressed on the telephone set and the communication being therefore interrupted.
detailed seminar report:
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