Browse Prior Art Database

On/Off Switching for Fault Tolerant System

IP.com Disclosure Number: IPCOM000117380D
Original Publication Date: 1996-Feb-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Beer, R: AUTHOR [+5]

Abstract

Where products are designed to offer 100% fault-tolerance and concurrent maintainability, the failure of a component requires it to be possible to remove it, and to fit a replacement without disturbing the operation of the system.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 61% of the total text.

On/Off Switching for Fault Tolerant System

      Where products are designed to offer 100% fault-tolerance and
concurrent maintainability, the failure of a component requires it to
be possible to remove it, and to fit a replacement without disturbing
the operation of the system.

      A typical product is arranged as a standard "4U" size EIA
rack-mounted unit with all components removable from either the front
or the rear of the rack.  A small operator-panel assembly housed at
the front of the unit contains an on/off switch and two LED
indicators.  The operator-panel is located outside the machine's RFI
shield (essential for compliance with international EMC and safety
regulations).  It is necessary to remove the operator-panel and RFI
shield when replacing other components.

      Experience from other products shows that the service engineer
might accidentally knock the on/off switch while the operator-panel
was temporarily removed.  Upon replacement it would then be in the
"off" position and so would shut down the fault-tolerant system.
This is unacceptable.

      The solution shown in the Figure uses a single, very low-power
CMOS chip on the operator-panel.  This chip takes its power from the
on/off control input pin of the machine power-supply.

      The power-supply considers its on/off input to be OFF when it
is below +5.0V and ON when above +5.0V.  The power supply monitors
this line and provides a tie-up resistor to a nominal +18V inter...