Electronic equipment housing

An electronic equipment housing provides easy access to electronic equipment via a hinged top panel and a clear plastic safety panel below it. Inside the housing are cable raceways located at the top front and top rear which are in line with raceways in adjacent housings to permit many cables to be contained inside the housings. The raceways and cables are positioned so as not to interfere with convection cooling inside the housings and with access to the equipment. Relatively high heat generating equipment such as power supplies are mounted to one side of the interior of the housing enabling separate fans to cool the power supplies using a single flow of air while other equipment in the housing is cooled by a separate flow of air drawn by other fans. Common system equipment is enclosed in the housing located at a predetermined one end of a series of adjacent housings. The common housing has a side mounted connector arrangement, with the connectors being mounted on swing out doors or bulkheads for ease of access. The connectors are organized to accommodate cables coming from other adjacent housings to the connectors which have the same length cables. The front and rear panels on all housings have horizontal slots that permit cooling air flow for cooling, and conductive screening behind the slots for minimizing radio frequency interference (RFI). In addition, the top, front and side removable panels have gaskets to suppress RFI signals.

BACKGROUND 
1. Field of the Invention 
This invention relates to packaging for electronic circuitry and more 
particularly to housings for packaging electronic equipment. 
2. Background of the Invention 
In the prior art, electronic computer circuitry and equipment have 
typically been packaged in metal housings or enclosures, different sides 
or panels of which are removable to gain access to the circuits and 
equipment in the interior of the housing. Alternatively, an entire housing 
cover is removed as a single piece from the top of the equipment housing 
to gain access to the circuits and other equipment inside. 
Power and signal cables to and between a group of housings in a computer 
system typically connect to connectors mounted at the rear of the 
housings. Various switches are also located on the rear of the housings. 
Access to and removal of printed circuit (PC) cards and other modules such 
as power supplies, disk drives, and fans are typically achieved by the 
removal of a front panel of such housings. 
There are many shortcomings with these prior art electronic equipment 
housings. For example, the rear housing cabling arrangement normally 
requires that the housings be spaced far enough from a wall to provide 
room for the cables, and so that access may be had to the cables and 
switches at the rear of the housings. This creates unused floor space that 
can add to certain inefficiencies. In addition, the cables normally 
situated on the floor behind the housings create certain hazards. The 
problem is made worse by the fact that the cables are usually made to a 
standard length and typically too long, thus requiring that the excess 
cabling be coiled or just lie in disarray. 
To minimize the wasted floor space, the equipment is sometimes located as 
close to the wall as possible. This has been found to create another 
problem of access to the cables and their connectors, switches and even 
the rear of housing accessed interior components. In such arrangements, to 
gain working access to the rear of the housings, the equipment must be 
temporarily moved further away from the wall which often creates other 
problems such as inadvertently disconnecting and/or damaging connectors. 
Access to printed circuit cards and other equipment through the front of a 
housing may be accomplished by removing its front panel if the housing is 
relatively high so that the interior can be accessed by a person while 
standing up. However, many modern housings are only two to three feet 
high. The result is that a person must assume a prone position to view the 
interior of the housing and to remove printed circuit cards and other 
modules therefrom. This has been found to be both inefficient and 
inconvenient. 
Another problem with some prior art housings is that printed circuit cards 
containing temperature sensitive components are sometimes mounted adjacent 
to heat generating equipment such as power supplies. Thus, the same 
cooling air is circulated over the printed circuit cards and the high heat 
generating component such as the power supplies. Where the air passes over 
the printed circuit cards first, the air is warmed before reaching 
components such as power supplies resulting in decreased cooling effect. 
To compensate for such cooling inefficiencies, either larger fans are used 
which require more space and use more power, or the maximum temperature of 
the room in which the equipment is located is lowered. 
Thus, there is a need in the prior art for an electronic equipment housing 
which can be located close to a wall to conserve floor space. In addition, 
there is a need for a way to more conveniently access printed circuit 
cards and most other equipment in the housing. Moreover, there is a need 
for a cabling arrangement which can minimize exterior cabling which still 
permits the use of standard length cables. Further, there is a need for an 
equipment arrangement in the housings that permits adequate cooling via 
convection and with the smallest possible cooling fans. 
SUMMARY OF THE INVENTION 
The aforementioned needs of the prior art are met by the modular electronic 
equipment housings of the present invention. The modular housing 
arrangement of the present invention permits the positioning of housings 
contiguous to each other in a computer system configuration, by simply 
removing the sides of the housings that are to be positioned adjacent to 
each other. The tops of each of these housings are hinged, thereby 
allowing for easy top access to vertically mounted printed circuit boards 
and other electronic components inside the housings. 
Common system electronic equipment such as disk drives and most 
input/output cable interfaces are mounted in a common equipment housing, 
while printed circuit cards containing computer circuitry such as 
processors and memory are mounted in a different housing. 
No cabling between individual ones of the novel housings lies on the floor 
behind the housings. AC power cables and some communication cables are 
located at the rear of and enter the housings through a cutaway. Also, 
cables to peripheral equipment such as printers are located at the rear of 
and enter the common equipment housing through a cutaway. This housing is 
located at one end of a row of housings in a system configuration. This 
arrangement simplifies access to peripheral equipment cable connections. 
Inside each PC card housing, there are cable raceways positioned parallel 
to the front panel and located at the top front and at the top rear of the 
housing. With housing side panels removed between contiguous PC card 
housings, the cable raceways in the housings are positioned to be 
coaxially aligned. Cables between circuits and other components inside the 
PC card housings and the common equipment housing are placed in these 
interior cable raceways. The cable raceways are positioned so that the 
cables therein do not interfere with convection cooling of the printed 
circuit boards and other electronic components, the flow of air from 
cooling fans, and with access to these PC cards and other components from 
the hinged top panel of the equipment housings. 
Input and output signal cables all connect to a bulkhead connector array 
located at one side of the common equipment housing. The bulkhead is 
divided into a plurality of swing out sections. The connectors are mounted 
on these swing out sections or doors that permit easy access to change or 
reposition connectors or bulkhead sections and interior wiring. In 
addition, the connectors are organized in an arrangement that permits the 
connecting cables from any one of the adjacent housings to be of a 
standard length and not require coiling due to excess cable. 
In PC card housings, the power supplies for the PC cards are mounted to one 
side of the housing. Fans are located to cool the power supplies and the 
printed circuit cards, by drawing air through horizontal slots contained 
in the front panel of the housing which exits through similar horizontal 
slots contained in the rear panel of the housing. In this arrangement, the 
air which passes over either the printed circuit cards or the power 
supplies does not pass over other components, so maximum cooling is 
achieved. 
The horizontal slots through the front and rear panels of the housings have 
conductive screening positioned behind and across them to minimize radio 
frequency interference (RFI) signals escaping from the interiors of the 
housings. In addition, the housings and the removable panels including the 
hinged housing top are painted with a conductive paint. All removable or 
opening panels have conductive seals, conventional in design, mounted 
thereon which contact the conductive paint to further minimize RFI signals 
from escaping from the housings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1 is shown a three dimensional view of a typical common housing 10 
and two adjacent printed circuit card housings 11 and 11A. In a small 
system configuration, there is one housing 10 and one housing 11. In 
larger system configurations there are more housings 11, of which only one 
such extra housing 11A is shown in FIG. 1. 
Housing 10 has a latched lift-off top cover 49 that can be easily opened to 
gain access to the interior of housing 10. Housings 11 and 11A have a 
hinged top cover 19 and underneath that a clear plastic cover 46. Housing 
11 is shown with its hinged metal top 19 and its internal hinged clear 
plastic top cover 46 open, with an exemplary printed circuit card 34 shown 
partially removed. Hinged top 19 is equipped with a mechanism (not shown) 
that permits it when opened to remain opened by itself, without the need 
for a support arm, until top 19 is closed. 
Card 34 connects to a cable 48 via an edge connector which is normally 
disconnected before card 34 is removed. Around the bottom side of hinged 
top cover 19 is an RFI gasket 15 which makes a good RFI seal with the top 
edges of housing 11 when top 19 is closed. To assist in RFI sealing, and 
with RFI suppression generally, the housings are all painted inside with a 
conductive paint. Front panels 14 as shown are mounted on the front of 
housings 10, 11 and 11A. The panels are easily removed to gain access to 
electrical components, such as fans, that need infrequent maintenance or 
replacement. These components are better shown in FIG. 2b. 
Housings 10, 11, and 11A all have removable side panels. Each has a front 
panel 14, a left side panel 12, a right side panel 13, and a rear panel 
54. When two housings are mounted adjacent to each other the side panels 
12 and 13 between them are removed, and the housings are bolted together 
in a conventional manner. 
In the configuration of FIG. 1, the left side panels 12 have been removed 
from housings 11 and 11A, and the right side panels 13 have been removed 
from housings 10 and 11. This leaves left side panel 12 on housing 10 and 
right side panel 13 on housing 11A, as shown. As discussed herein, this 
permits inter-housing cables to be positioned within the internal cable 
raceways 17 and 18 contained inside housings 10, 11, and 11A. 
Left side panel 12 on housing 10 encloses a bulkhead connector interface 55 
shown in detail in FIG. 2b. As discussed herein, interface 55 is where 
cables 25 with connectors entering housing 10 connect to mating connectors 
on the cables that are distributed to housings 10, 11, and 11A. 
Located around the underside of each of the hinged housing tops 19 of 
housings 11 and 11A there is RFI gasket 15 which makes an RFI seal with 
the top of housings 11 and 11A to minimize RFI emissions when the tops 19 
are closed. Similarly, located around the inside edge of front panel 14, 
right side panel 13, left side panel 12, and rear panel 54 of housings 10, 
11, and 11A there are also RFI seals (not shown) which make an RFI seal 
respectively with the front, left, right and rear sides of the housings 
when they are fastened to the housings. When housings 10, 11, 11A are 
bolted together with some of their side panels 12 and 13 removed, as 
described above, there is still an RFI tight seal. As mentioned above, no 
further aid in the RFI suppression, the interiors of all of the housings 
10, 11, and 11A, including their tops 19 and sides 12, 13, 14 and 54 are 
painted with a conductive paint. 
Inside housings 11 and 11A are two cable raceways 17 and 18 as shown. Cable 
raceway 17 is located at the top front of housing 11 and parallel to the 
front of the housing. Cable raceway 18 is located at the top rear of 
housing 11 and also parallel to the front of the housing. When two or more 
housings 11 and 11A are bolted together without side panels 12 and 13 
between them in the computer system configuration of FIG. 1, the top front 
cable raceways 17 in adjacent housings 11 and 11A are placed in coaxial 
alignment with each other. Similarly, the top rear cable raceways 18 in 
adjacent housings 11 and 11A are placed in coaxial alignment with each 
other. This provides front and rear cable paths for inter-housing sets of 
cables 36 and 37 as shown in FIG. 2b) to and between the printed circuit 
cards 33 and 34 and other components such as power supplies 38 inside the 
adjacent housings 10, 11 and 11A that are completely enclosed. This 
arrangement provides easy cable access to the inter-housing cables without 
having to go behind the housings 10, 11 and 11A. In addition, by having 
the inter-housing sets of cables 36 and 37 located inside of the housings 
10, 11, and 11A not only are the number of cables positioned behind 
housings 10, 11 and 11A minimized but, importantly, these sets of cables 
36 and 37 are shielded by being placed inside the housings 10, 11 and 11A 
thereby providing additional suppression of RFI signals caused by signals 
on the wires within the cables. 
Also located inside the top of housings 11 and 11A, underneath hinged top 
cover 19, is a safety top cover 46 which is made of clear plastic. Top 
cover 46 is equipped with a conventional tool operated lock which is 
installed into a hole 47. Only maintenance personnel have a key to open 
plastic top cover 46 for maintenance purposes such as removing PC cards 33 
and power supplies 38. Other non-maintenance personnel are thereby 
excluded from gaining access to the electronics for safety purposes since 
there are exposed terminals with voltages thereon. However, the 
non-maintenance personnel are able to see various operational status 
lights 34 beneath the clear plastic cover 46. 
Front panels 14 have a plurality of horizontal slots 16 on the front of 
housings 10, 11 and 11A. Behind the slots 16 is a conductive screen 
depicted by a grid pattern in FIG. 1 which provides RFI shielding. 
Similarly, there are slots 16 through rear panels 54 on the rear of 
housings 10, 11 and 11A which are also RFI shielded by conductive 
screening. These horizontal front and rear slots 16 provide a passage for 
air to be drawn in through the front slots 16 and out through the rear 
slots 16 which cool the printed circuit boards 33 and other electrical 
components such as power supplies located inside of housings 10, 11 and 
11A. 
FIGS. 2a and 2b are three dimensional views of the interior elements of 
adjacent equipment housings 10, 11 and 11A. Only the three housings are 
shown in FIGS. 2a and 2b, but any number of housings may be bolted 
together depending upon the particular computer system configuration. 
Also, only two types of representative housings 10 and 11 are shown, but 
those skilled in the art can mount other types of electronic equipment in 
the housing in accordance with teaching of the present invention. 
The frame structure, the hinged housing top 19, and left, right, front, and 
rear panels 12, 13, 14, and 54 have been removed from housings 10, 11, and 
11A in FIG. 2b so that other details of the electronic equipment housing 
arrangement of the present invention may be seen. While the mechanical 
parts of housings 10, 11, and 11A as described above with reference to 
FIG. 1 are basically the same, there are some differences other than those 
described with reference to FIG. 1. For example, inside housings 11 and 
11A are mounted, printed circuit card trays or containers 32, cooling fans 
39 and 40, and power supplies 38. Inside housing 10 are mounted common 
system components such as a floppy disk drive 23, an operators panel 27, a 
power supply 20, a tape unit 26 containing tape cartridges to back up 
daily transactions processed by the computer system, and a bulkhead 
connector interface 55. Interface 55 shown in greater detail in FIG. 3, 
provides cables 25 to mating connectors attached to cables 36 and 37 which 
are connected to the circuits and other components inside housings 10, 11 
and 11A. 
Bulkhead connector interface 55 is divided into three swing out doors or 
bulkhead sections 28, 29 and 30. Door or section 28 is hinged and swings 
out to the left as shown, while section or door 29 is hinged at its right 
edge and swings out to the right. The larger section or door 30 is hinged 
and swings out and down. As mentioned previously, these swing-out doors or 
bulkhead sections 28, 29 and 30 permit access to the connectors on cables 
36 and 37 to change them, move them, or to change cable wiring to them. In 
a small system configuration, only swing-out door or section 30 is 
utilized. For larger system configurations swing-out doors or sections 28 
and 29 are added as required to handle additional cable connector 
connections. 
As shown in FIG. 2b, each of the swing-out doors 28, 29 and 30 has a 
surface that is saw-tooth in shape. This saw-tooth shape creates a number 
of surfaces 59 which are angled to face downward on the outside of doors 
28, 29 and 30. Through these surfaces 59, are punched rows of cutouts 
designed to latch and hold connectors on the ends of cables in the set of 
cables 36 and 37, such as exemplary cable. With the connector 31 on the 
end of cable 57 latched to a surface 59, cable 57 bends upward over the 
top of the equipment inside of housing 10. Similarly, the angle of 
surfaces 59 causes those cables 25 connected to connectors, such as 
connector 31, which are latched at surface 59 to bend downward. 
Cables 25 enter and exit housing 10 via a cutback or notched portion 51 at 
the edge of base pan 50 of housing 10. When left side panel 12 is 
installed on housing 10, connector interface 55 cannot be seen. The result 
of using angled surfaces 59 as cable connector interface 55 insures that 
there are no sharp bends in cables 25, 36 or 37. An example of latching 
connector housings that latch to cutouts through surfaces 59 and latch to 
housings containing connectors of cables 25 is disclosed in U.S. Pat. No. 
4,634,203, issued Jan. 6, 1987. 
In addition, a rear swing-out door 22 or bulkhead section is provided at 
the rear of common equipment housing 10 for connecting cables to and from 
peripheral equipment (not shown), such as a printer, to electronic 
equipment inside housings 10, 11, and 11A. Cable 42 included in the set of 
cables 37 is shown connected to the inner side of bulkhead door 22. 
Bulkhead door 22 discussed herein in greater detail with reference to FIG. 
4 and is assembled in the manner same as doors 28, 29 and 30. 
Base pan 50 of common equipment housing 10 also has a second notched or 
cutback 67 on its rear edge shown in FIG. 4. Cables from peripheral 
equipment such as printers enter housing 10 behind the removable rear 
panel 54 through cutback 67 and connect to mating connectors latched to 
the auxiliary bulkhead section connector door or bulkhead 22. 
Housings 11 and 11A are of identical construction and are used to house 
vertically mounted printed circuit (PC) card trays 32 into which are 
inserted PC cards 33. Printed circuit card trays 32 include plastic edge 
guides (not shown) that bind the edge of the cards to prevent them from 
accidentally slidding down into the card tray and damaging the cards and 
the connectors located at the bottom of trays 32. 
As discussed earlier each of housings 11 and 11A include the cable raceways 
17 and 18. The front cable raceway 17 and the rear cable raceway 18 in 
each of the housings 11 and 11A are positioned in coaxial alignment with 
each other when housings 11 and 11A are arranged contiguous to each other 
as shown. As previously mentioned, when two housings 11 and 11A are bolted 
together in a given system configuration, they have no side panels 12 and 
13 between them. This allows the sets of cables 36 located in front cable 
raceways 17 and the set of cables 37 located in rear cable raceways 18 to 
pass unimpeded between housings 10, 11 and 11A as shown. The position of 
cable raceways 17 and 18 in housings 11 and 11A, and the sets of cables 36 
and 37 therein, do not interfere with insertion or removal of PC cards 33 
and 34 in or from PC card trays 32. Raceways 17 and 18 also do not 
interfere with the flow of fan blown cooling air through PC cards 33. In 
cable raceways 17 and 18, are mounted cable clamps 35 that are used to 
hold the cables included within the set of cables 36 and 37 in the 
raceways, yet let them fan out to the printed circuit cards 33 in card 
tray 32. 
In housings 11 and 11A, those cables of the sets of cables 36 and 37 
connecting to a particular PC card 33 fan out from cable raceways 17 and 
18 and the cable clamps 35 therein generally in line with a particular PC 
card 33. In this way, the cables do not interfere with other PC cards, and 
particularly the insertion or removal of same. Those cables that connect 
to a particular PC card 33 have PC edge connectors mount thereon that plug 
onto the edge of the particular PC card in a manner well known in the art. 
When it desired to remove a PC card, the edge connectors are unplugged and 
the PC card is withdrawn vertically, as shown for PC card 34 in FIG. 1. 
This organization of cable raceways 17 and 18 and cables 36 and 37 therein 
does not interfere with any of the PC cards 33. 
Power supplies 38 which supply power to PC cards 33 in each of housings 11 
and 11A are located to the right side of the inside of the housings as 
shown in FIGS. 1, 2a and 2b. Power supplies 38 are mounted vertically 
which enable them to be also accessed for maintenance and replacement by 
lifting hinged top 19, and safety cover 46 on each of housings 11 and 11A. 
Air circulating fans 39 and 40 are mounted to the front of housings 11 and 
11A as shown in FIG. 26 to provide cooling air respectively to power 
supplies 38 and the printed circuit cards 33. Fans 39 pull air in through 
the slots 16 in the front panel 14 of FIG. 1) of housings 11 and 11A, 
which passes over the power supplies 38 to cool them, and exits the inside 
of housings 11 and 11A by the slots 16 through the rear panel 54 of FIG. 
1. Fans 40 pull air in through the horizontal slots 16 in the front panel 
14 of FIG. 1 of housings 11 and 11A which passes through the PC cards 33 
to cool them, and exits the inside of housings 11 and 11A via the slots 16 
through the rear panel 54 of FIG. 1. With this configuration, the same air 
is not used to cool both power supplies 38 and PC cards 33 as in the prior 
art. To access the cooling fans 39 and 40 the front panel 14 of FIG. 1 is 
removed. Since, cooling fans very seldom need replacement, there is little 
inconvenience of having to access housings 11 and 11A through front panel 
14. 
At the bottom of the inside of housings 11 and 11A are located power 
distribution units 44 which distribute AC power to the power supplies 38 
and other equipment, such as fans 39 and 40. Also located at the bottom of 
the inside of housings 11 and 11A, is a flap chassis 45 to which the 
connectors of special cables 61 connect. These special cables 61 and an AC 
power cable (not shown) enter the rear of the housings 11 and 11A through 
a cutback (not shown) located on the rear edge of base pan 62 and 63 
respectively like cutbacks 51 and 67 on base 50 of housing 10. 
FIG. 3 shows in a diagrammatic form a front view of housings 10, 11 and 11A 
with inter-housing sets of cables 36 and 37 going from PC cards 33 in card 
trays 32 to swing-out doors 28, 29 and 30 of bulkhead connector interface 
55 in housing 10. In this Figure, the door or section 28 is located behind 
door section 29 as can be seen from FIG. 2b. Normally the sets of cables 
36 and 37 lie in the cable raceways 17 and 18, but they are shown in an 
elevated position in FIG. 3 to aid in understanding the cabling 
arrangement of the present invention. 
It can be seen that cable 48 is connected between PC card 64 in housing 11 
which is located closest to connector interface 55 to one of the angled 
surfaces 59 at the lowest level of seing out door 30. Cable 53 is 
connected between PC card 66 located in housing 11 farthest from connector 
interface 55 to one of the angled surfaces 59 at the highest level of 
swing out door 30. Cable 52 is connected between an intermediate PC card 
65 in housing 11 to one of the angled surfaces 59 at a middle level of 
swing out door 30. Cable 52 is latched to the middle level surface 59 of 
swing-out door 30 because of the distance of its other end from housing 
10. 
This cable arrangement allows for one length of cable to be used between 
housing 11 and door 30 of connector interface 55 in housing 10. FIG. 3 
illustrates previously described angular orientation of the connectors on 
the ends of sets of cables 36 and 37 latched to the inner side of doors 
28, 29 and 30 of connector interface 55, and of the connectors on the ends 
of cables 25 external to housing 10 mated to cables 36 and 37. 
It can be seen in FIG. 3 that cables 56, 57 and 58 of the sets of cables 36 
and 37 going from PC cards 64A, 65A and 66A of housing 11A to doors 28 and 
29 of bulkhead connector interface 55 in housing 10 are similarly 
arranged. 
FIG. 4 shows a top view of the cabling arrangement of the sets of cables 36 
and 37 inside housings 10 and 11. It is seen how exemplary cables 63 and 
64 edge connect between a PC card 65 and a mating connection through swing 
out door 30 of connector interface 55. In FIG. 4, door 30 is located below 
doors 28 and 29 and therefore, only a very small part is visible. Cables 
52 and 52-1 and all other inter-housing cables terminating in housing 11 
are of the same length as mentioned previously. The cable 52-1 which has a 
connector on one end located close to the center or middle of PC card 65 
has its other end connected or mated to door 30 at the bulkhead position 
located closest to the front of housing 10. The cable 52 which has a 
connector on the end located closest to the front edge of PC card 65 has 
its other end mated to door 30 at a bulkhead position located further 
toward the rear or housing 10. Thus, the arrangement provides 
substantially equal distribution of cable lengths so that each cable, has 
a similar amount of managable cable, excess. Although this cable 
arrangement is only shown with a couple of representative cables, it 
applies to all of the cables included within inter-housing sets of cables 
36 and 37. 
By coupling the previously described routing of inter-housing sets of 
cables 36 and 37 to swing out doors 28, 29 and 30, as described with 
reference to FIGS. 3 and 4 as a function of which cable raceway they are 
in and where on a PC card they connect, the result is that one length 
cable may be used for all cables from one of housings 11 or 11A without 
the problem of excess cable length. 
Returning to FIG. 4, swing-out auxiliary connector bulkhead 22 is shown in 
its normal vertical position by solid lines, and shown in its swing-out 
position by dotted lines. As previously described, door 22 is used for 
making cabling connections to peripheral equipment. Thus, cable 21 from a 
piece of peripheral equipment such as a printer and connects via bulkhead 
22 to cable 42 which connects to circuitry internal to housings 11 or 11A 
that will transmit or receive signals to or from the peripheral equipment. 
When bulkhead 22 is in its swing-out position, the connector on cable 42 
can easily be accessed to move the connector or to change wiring therein. 
Also shown in FIG. 4 is cutout 67 located at the rear edge of base pan 50 
of housing 10 through which cables to/from peripheral equipment pass. 
While what has been described hereinabove is the preferred embodiment of 
the invention, it will be obvious to those skilled in the art that 
numerous changes may be made without departing from the spirit and scope 
of the invention. For example, the cooling fans may be mounted at the rear 
of the housing instead of the front to improve noise silencing. Also, 
different equipment arrangements may be used inside the housings. In 
addition, protrusions may be spaced along the top edge of the cable 
raceways to help position cables as they exit the raceway to edge connect 
to PC cards.