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Implementation of Logic Book/Cage Keys

IP.com Disclosure Number: IPCOM000120075D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 7 page(s) / 303K

Publishing Venue

IBM

Related People

Corfits, WD: AUTHOR [+3]

Abstract

A typical central electronics complex (CEC) (illustrated in Fig. 1) consists of a logic cage 1 which is designed to accept "Books" 3 that contain the logic for the system. Books 3 consist of logic cards with added covers that provide four rails 4 for guiding the assembly into cage 1, slots 2 and electrical and mechanical protection for the logic card electronics. Books 3 have electrical connectors (not shown) that plug to the logic cage backplane card 21 and allow the transfer of power and logic signals throughout the system. The lack of uniformity of the connectors and lines going to them may cause physical and/or electrical damage if a book is plugged into the wrong logic cage slot.

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This is the abbreviated version, containing approximately 29% of the total text.

Implementation of Logic Book/Cage Keys

      A typical central electronics complex (CEC) (illustrated
in Fig. 1) consists of a logic cage 1 which is designed to accept
"Books" 3 that contain the logic for the system. Books 3 consist of
logic cards with added covers that provide four rails 4 for guiding
the assembly into cage 1, slots 2 and electrical and mechanical
protection for the logic card electronics.  Books 3 have electrical
connectors (not shown) that plug to the logic cage backplane card 21
and allow the transfer of power and logic signals throughout the
system.  The lack of uniformity of the connectors and lines going to
them may cause physical and/or electrical damage if a book is plugged
into the wrong logic cage slot. A method is needed to "key" each type
of book so that it can only be inserted in a cage slot that is
matched to the book connector type and electrical line location, thus
preventing damage to the book or the cage from incorrect
installation.

      A mechanical keying system between two objects is shown in Fig.
2.  Object A, which fits into object B, has added to it a male
feature 40; object B has a mating female feature 41 into which male
feature 40 fits.

      It is obvious from Fig. 2 that no object A, with feature 40
added, will fit in any object B without female feature 41.  Object A
with feature 40 is, therefore, uniquely keyed so that it can only be
inserted into any object B having feature 41.  Note that the simple
key system described above is not truly exclusive, as any object A,
without feature 40, may be inserted into object B whether or not
object B has feature 41.  The keys are limited to one exclusive
combination.  To allow more combinations and guarantee that they are
exclusive, there must be provision for more than one male feature 40
on object A and more than one female feature 41 on object B.  A truth
table listing all combinations of feature 40 on object A will show
the properties of the keying concept.  A truth table is constructed
with one vertical column for each variable and one horizontal row for
each combination, where the number of rows is equal to 2 raised to
the N power (where N equals the number of columns, or variables).
The truth table for a system with three possible key positions
(variables) on the tops of objects A and B is shown in Fig. 3.

      There are eight individual key combinations.  For example, a
male feature 40 in position C on object A --the combination in row
2-- can only be inserted in an object B having a female feature 41 in
position C.  It is obvious by inspection that using every combination
will result in a non-exclusive keying system; there are three
combinations (rows 4, 6, and 8) where object B having female features
41 in the positions noted will allow the insertion of object A having
one male feature 40 in position C.  Note also that an object A keyed
for combination 1, with no male features 40, will insert in any
object B keye...