Emergency power shutdown system for educational laboratory

Claim 1

An emergency power shutdown system for an educational laboratory, comprising: a power supply system; a plurality of items of potentially dangerous educational equipment, each item connected to be operational only with power from the power supply system; a portable transmitter unit adapted to be carried by an instructor in the laboratory, the transmitter unit having a transmitter capable of sending an RF signal, the transmitter unit also having a portable electric power supply, the transmitter being normally disconnected from the portable electric power supply except when it is activated to send an RF signal; a control unit fixedly mounted in an enclosure in the laboratory, the control unit including a receiver capable of receiving the RF signal from the transmitter, the receiver including means for sensing a signal from the transmitter and for activating a first relay only upon receipt of said signal, the first relay being open and closed in response to the receipt of the RF signal sensed by the sensing means, the first relay having first and second and third control lines, the first control line being connected to the second control line when the first relay is open and the first control line being connected to the third control line when the first relay is closed; and a relay-operated shutdown unit mounted in the enclosure and forming a part of the power supply system, the shutdown unit having a manually operated first switch operatively connected to a coil, the coil operating a second relay connected into the power supply system, the coil also being operatively connected to two of the first and second and third control lines, the coil being actuated by either the manually operated first switch or by actuation of said first contact to open the second relay to interrupt the supply of power through the power supply system, the shutdown unit also having a manually operated second switch to actuate the coil and close the second relay to restore the supply of power through the power supply system.