Terminator assembly for interconnecting computer devices

A compact terminator for interconnecting computer devices with each other and with peripheral equipment having contact ends to be interconnected with connectors. The contacts are interconnected on a circuit board employing thick film circuitry mounted thereon. The contacts are press fitted in plated through holes on the circuit board and form male or female connectors at one end. The device may be a differential or single ended type.

BACKGROUND OF THE INVENTION 
This invention relates in general to computer systems and, in particular, 
to a device for interconnecting a host (source) computer with other 
(object) computers or peripheral equipment. 
More specifically, this invention relates to a terminator for attaining 
compatibility between terminals, computers, printers and other equipment 
from different manufacturing sources. 
The computer industry has introduced products from a multitude of different 
manufacturers involving many designs of disc drives, small computers, 
printers, terminals and related systems. Because of the presence of so 
many types of equipment, compatibility between systems from diverse 
sources has not been realized, with the result that many types of 
computers, peripheral equipment or software cannot be used with other 
products from another source. 
Because code compatibility between diverse peripheral devices and computers 
does not exist, users have only been able to interconnect computers with 
peripheral equipment or other computers to a limited extent. The computer 
industry has failed heretofore to provide generally universal 
compatibility to enable the user of computer equipment to select and use 
products from a wide range of manufacturers. The failure to permit 
interchangeability of peripheral equipment with many types of computers, 
or computers with other computers, further makes the cost of software more 
expensive and less usable from machine to machine. 
To solve this problem, numerous manufacturers and others in the computer 
industry set standards under the American National Standards Institute 
(ANSI) and developed specifications for effective information interchange. 
The circuits specified by ANSI provide code compatibility for use between 
a wide range of computers and with other computers or with peripheral 
equipment. Software programming becomes less expensive and its use can be 
shared by more systems than in previous equipment where compatibility 
could not exist. 
SUMMARY OF THE INVENTION 
It is therefore an object of the invention to attain compatibility between 
terminals, computers and related equipment. 
Another object of this invention is to insure code compatibility between 
diverse peripheral devices. 
A further object of this invention is to attain code compatibility through 
the use of an inexpensive and physically compact device. 
Still another object of this invention is to provide a computer terminator 
for code compatibility employing in part thick film circuitry. 
These and other objects are attained in accordance with the invention 
wherein there is provided a terminator assembly capable of meeting all 
applicable standards of the American National Standards Institute (ANSI). 
The device of the invention eliminates the use of discrete resistors with 
the result that a relatively bulky structural configuration is eliminated 
for superior results in use. The device of the invention employs thick 
film technology, such that electrical circuits are provided to permit a 
more universal interchange between computer devices.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 1-8, there are illustrated embodiments of the 
pluggable terminator of the invention for interconnecting small computers 
with each other and with low to medium performance, intelligent 
peripherals in the form of discs, either rigid or flexible, magnetic tape 
devices, printers, and the like. Although the invention is not intended to 
be so limited, the pluggable terminator described herein conforms to the 
specifications set forth in a draft proposed by American National Standard 
Institute under the development by a Task Group X3T9.2, including 
variations as specified by various computer manufacturers, as set forth in 
the publication entitled Small Computer System Interface, ANSC 
X3T9.2/82-2, Revision 6 (Feb. 14, 1983). 
The invention of the application is intended to be operated at rates up to 
approximately 4 megabytes per second and provides host computers with 
device independence. The invention may be used with disc drives, tape 
drive printers and communication devices of different types for 
interconnection with a host computer(s) without modifications of system 
hardware or software. 
The terminator is designed to operate over distances of approximately 15 
meters and data rates at 4 microbytes per second. Although the specific 
embodiments disclosed in FIGS. 1-8 conform to the standards for 
information interchange as specified by the American National Standards 
Institute, it is within the scope of the invention to modify the 
specifications or terminals in accordance with existing standards or 
design considerations. 
The embodiment of the terminator described with reference to FIGS. 1-6 is 
directed to an internal terminator 2 of a differential form. Although the 
terminator 2 is shown having upper female contact ends and lower male 
ends, the invention is not intended to be so limited. The terminator of 
the invention may also employ all male pins on both connector sides of the 
terminator, all female contacts on both sides of the terminator, or male 
and female ends in opposite orientation than as shown in FIGS. 1-4. 
The terminator of FIGS. 1-4 basically includes a female insulator 4, header 
5, an insulative male shroud 6, a PC board 10 having thick film circuitry 
applied thereto, and a plurality of bifurcated contacts 12, although other 
contact forms can be used. In accordance with the ANSI specifications, 
fifty contacts 12 are arranged as pairs in two rows along the length of 
the terminator 2, as best seen in FIG. 3. Each pair of contacts 12 is 
disposed in compartments 14 within female insulator 4, such that each pair 
is separated by internal wall 16. The upper portion of the female 
insulator 4 is provided with openings 18 adjacent each contact to act as a 
guide to accept male pins. The pins of a device or cable assembly being 
inserted into the female openings 18 engage the contact ends 22 of contact 
12. The female ends 22 can be formed as cantilevered, bifurcated portions 
of the contact. The contact ends 22 resiliently embrace the inserted pin 
to provide an electrical connection. The contacts 12 may be mounted on a 
header 5, PC board 10 and provide either male, female, or both contact 
interconnects in certain uses of the device. 
The contacts 12 extend through holes 24 in the PC board 10 and provide male 
pins or tails 30 at the opposite side of the terminal from the female 
ends. The open ended male shroud 6 surrounds the tails 30 and is connected 
to the female header 5 by snap-on portions 32 that interfit with male 
shroud shoulder 20. The female insulator 4 and male shroud 6 form a 
compartment 34, in which the thick film resistor PC board 10 is 
positioned. 
Referring to FIGS. 5 and 6, sides 1 and 2 of the PC board 10 are best 
illustrated and are respectively designated by reference numerals 10b, 
10a. Side 10b of the PC board 10 is formed with fifty contact holes 24 
extending through the board and forming fifty places provided with solder 
pads 36. The electrical circuit on both sides 10a and 10b is comprised of 
metal foils and/or films to form conductive areas, and polymer 
compositions applied by a known thick film process to form resistive 
paths. 
Thirty-six of the pads 36 are connected by a conductive trace 38a, 38b, to 
conductive outer and inner trace areas 40a, 40b. A thick film, screened 
resistor 50 is connected between each pair of conductive trace areas 40a, 
40b, to form an electrical circuit therebetween with press fit section on 
lower portion of contacts 12. The resistors 50 are laid as a polymer 
composition on the PC boar through the well-known thick film process, and 
the resistors 40 are formed from an appropriate polymer and the like. Each 
of the resistors on side 10b possesses a resistance of 150 ohms.+-.5%, and 
extend between adjacent trace areas 40a and 40b. As seen in FIG. 5, two 
pairs of end holes of pads 36 on side 10b are not connected to the 
resistors, as are four pairs 52 near the central portion of the PC board. 
Another central pair of pads 54 is also not connected to the resistors 50. 
In FIG. 5, eighteen resistors 50 are applied to side 10b. 
In FIG. 6, side 10a of the PC board 10 is illustrated in which elongated 
conductive tracings 70a, 70b are also applied along opposed borders of the 
PC board 10. One end pair of solder pads 72 is electrically connected to 
the lower border tracing 70b by a conductive strip 72a, as is one of the 
opposite end pairs 74 by strip 74a. One central pair of the solder pads 76 
is conductively connected to the upper conductive border tracing 70a. 
Three additional pairs 78 of solder pads in the central portion of the PC 
board are further connected by respective conductive tracings to the lower 
border 70b. Each of the remaining pairs of solder pads 82 are electrically 
connected by tracings to conductive trace areas 80a and 80b. A series of 
polymer resistors 84 applied as composition, extend between either of the 
border portions 70a, 70b, and a trace area 80a and 80b respectively. The 
resistors each have a resistance of 330 ohms.+-.5%, 1/16 watt. Side 10a of 
the PC board is likewise formed through a polymer thick film technology in 
a known manner to form the resistors for the circuit on both sides of the 
PC board. The use of thick film significantly reduces the size of the 
terminator in comparison to other techniques employing discrete resistors. 
On side 10a, 36 resistors are present. 
The terminator 2 is in an eight-port, daisy chained bus which includes the 
following features. The terminator can be used with single and multiple 
host computer systems. The bus contention is handled by distributed 
arbitration on a prioritized basis, as required by ANSI standards. The 
terminator can accommodate multiple peripheral device types with 
asynchronous communication of up to 1.5 MBytes/sec., at 15 meters cable 
length and synchronous communication of up to 4 MBytes/sec. at 15 meters 
cable length. There can be multiple overlap of peripheral device 
operations and direct copy between peripheral devices, as outlined in the 
ANSC X3T9.2/82-2 specification. 
The unit is oriented toward intelligent peripheral devices and 
communication of the buses is allowed only at two bus devices at any time. 
There is a maximum of eight bus devices and each port is attached to a bus 
device, e.g. peripheral device controller or host computer. The terminator 
of the invention is capable of conforming to ANSI specifications with a 
significantly smaller and less expensive unit as compared to the bulkier 
devices using discrete resistors, as outlined in the ANSC X3T9.2/82-2 
specification. 
Referring now to FIGS. 7 and 8, there is illustrated another embodiment of 
the terminator of the invention of a single ended type. The embodiment of 
FIG. 2 is an internal terminator and may be provided with a shroud, 
housing and contacts of a similar design as described with reference to 
FIGS. 1-6. It should be noted, however, that other contacts, regardless of 
whether male or female ends, may be interchangeably used, dependent on 
desired results. 
The PC board 10' of the embodiment of FIGS. 7 and 8 is identical to that 
described with reference to the preceding embodiment and includes fifty 
holes for receiving the contacts (not shown) and arranged in two rows as 
pairs in the manner as the previous embodiment. Sides 100a and 100b of the 
PC board 10' include an electrical circuit also formed using a thick film 
technique. The holes in the PC board on both sides are surrounded with 
conductive solder pads on both sides. In FIG. 7, one row 102 of solder 
pads and contacts are not interconnected. The adjacent row 104 of solder 
pads is connected by conductive tracings 104a from each end with the 
exception of central solder pads 105 comprising pads 105a, 105b, 105c and 
105d. 
On opposite side 100a of the PC board, which is a view through side 100b, a 
conductive tracing strip 110 is applied as an elongated strip at one 
border portion. A second elongated strip 112 is applied at the opposite 
lower border portion. The border strip 112 is formed at its end portions 
as a plurality of separated, non-connected sections 112a of equal length 
except for section 114a. 
Nine solder pads 122 in row 102' from each end of the PC board are 
conductively connected to conductive tracings 124 and 126 positioned on 
opposite sides. The corresponding solder pads 122 in row 104' do not form 
a circuit with the conductive areas 124 and 126. One pair of solder pads 
130, 132 in rows 102, 104 are connected by a conductive trace 131 and, in 
turn, to an adjacent solder pad 134 in row 104'. Pads 130, 132 and 134 are 
connected by conductive trace 131. Pads 105a' and 105c' on side 100a, 
which correspond to the holes of pads 105a and 105c on side 100b, are 
electrically connected to an adjacent pad in row 102' by a tracing to 
continuous border tracing 110. The solder pad 138 adjacent to solder pad 
105b' in row 102' is coupled by a pair of tracings 140 to the central 
portion of broken border tracing 112. The remaining 105d', 105e' and 105f' 
are electrically connected to their adjacent pairs 142 in row 102'. 
Electrical resistors 150 formed from a polymer and applied by thick film 
printing technique form an electrical circuit connection between trace 
areas 124 and the continuous border tracing 110. Similarly, resistors 152 
extend between the trace areas 126 and a respective portion 112a of strip 
112. The resistors 150 possess a 330 ohm resistance, while resistors 152 
are 220 ohms. Side 100a accordingly includes thirty-six resistors to form 
a terminator to interconnect computer devices in a manner to conform to 
ANSI specifications. 
In the foregoing description, the invention of the application has been 
described with two internal terminators of a differential and single ended 
type. The principles of the invention can equally be used with external 
terminators of a single ended or differential type. Further, external and 
internal terminators constructed in accordance with the invention can 
include shielding means. An external terminator may be constructed in 
accordance with the invention by removal of male shroud 6 and contact ends 
30. 
While the invention has been described with reference to preferred 
embodiments, it will be understood by those skilled in the art that 
various changes may be made and equivalents may be substituted for 
elements thereof without departing from the scope of the invention. In 
addition, many modifications may be made to adapt a particular situation 
or material to the teachings of the invention without departing from the 
essential scope thereof. Therefore, it is intended that the invention not 
be limited to the particular embodiments disclosed as the best mode 
contemplated for carrying out this invention, but that the invention will 
include all embodiments falling within the scope of the appended claims.