Guildline 6564, Техническое руководство

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Section 4
TM6564-C-00
26 April, 2011
4-3
The second method for protection is the ‘close gate’ lines to the decoder circuits. The
control circuit will allow these gates to open only if the series protection line is complete to
ground. One of the contacts on each relay is connected in series, and will complete the
series protection circuit only if all the relays on the line are in the clear position. Thus, no
relay on the CHANNEL can be closed if any other relay on the CHANNEL is already
closed. These series protection lines are brought out to terminals on the rear panel. Thus if
more than one scanner is used in a large system and these terminals are connected together,
all units in the system will be protected.
The third protection mechanism to protect devices from damage is not shown on the
diagram but is part of the control logic circuit. This is the requirement that two push-
buttons on the front panel must be pressed at the same time for any relay to actuate. These
would be the CHANNEL button and any of the 16 relay selector push-buttons. This is to
help prevent accidental operation. It takes two hands to operate the scanner from the front
panel.