Browse Prior Art Database

5100A Tempest Filter for 8-Port Output

IP.com Disclosure Number: IPCOM000120382D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 98K

Publishing Venue

IBM

Related People

Cox, RE: AUTHOR [+2]

Abstract

This article describes a very compact eight-channel signal filter design which takes the signals from an RS-232C 79-pin adapter card connector on the IBM RT PC* and distributes them to a similar 79-pin connector on the I/O panel after filtering.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

5100A Tempest Filter for 8-Port Output

      This article describes a very compact eight-channel
signal filter design which takes the signals from an RS-232C 79-pin
adapter card connector on the IBM RT PC* and distributes them to a
similar 79-pin connector on the I/O panel after filtering.

      Normal filter designs utilize in-line filtering connectors or
similar means to remove potential comprising emanations due to
electromagnetic interference from getting outside the TEMPEST
enclosure in which electronic equipment is placed.  In some cases,
however, this approach is not possible due to the requirement to
package multiple filters in limited available space, without
increasing the enclosure size.  The problem was solved by connecting
the adapter card 79-pin connector input B to its mating 79-pin output
A and distributing the signals equally to two identical flat cables
C, at 36 conductors each for a total of 72 with 7 lines not used.
Each cable carries 4 channels of 9 signals each; and mating each
cable to a connector on two identical filter PC boards D containing
filter networks of 4 channels each, and which leave the PC boards
through a connector E on each.  The connector E mates with two rows
of filter pins contained in a filter block assembly that forms an EMI
TEMPEST bulkhead between the inside of the RT PC and the outside
filtered area which is fully enclosed to ensure that no comprising
emanations are emitted outside the RT PC.  Within this filtered area
the two rows of filter pins F on the filter block are connected to
two more connectors which are soldered to a special transition PC
board H, the said two rows of filter pins being on outboard edges of
the PC board at 36 signals and 4 channels on each.  The signals are
distributed on the transition PC board H by utilizing printed
cir...