Protector

A protector for use in a telecommunications system to establish an electrical connection between two lines includes a base and at least two line terminals extending from one surface of the base. A ground terminal also extends from the one surface of the base and is spaced from the two line terminals. A circuit board is mounted on another surface of the base and has electrical paths on it leading to the at least two line terminals and to the ground terminal. An overload detector is mounted on the circuit board and establishes an electrical connection between the at least two line terminals by way of the electrical paths in normal operation and establishes an electrical connection between at least one of the at least two line terminals and the ground terminal by way of the electrical paths in the event of an overload condition. A fail short may also be provided to establish a permanent electrical connection between the at least two line terminals and the ground terminal if the overload condition exceeds the rating of the overload detector.

FIELD OF THE INVENTION 
The present invention relates to protectors and in particular to a 
protector for use in a telecommunications system to terminate an 
electrical connection between two lines in the telecommunications system 
in the event of an overload condition. 
BACKGROUND OF THE INVENTION 
Protectors to isolate facilities and/or telecommunications equipment within 
the facilities from external telecommunications lines in the event of an 
overload condition are well known. Protectors of this nature are often 
located in external boxes where the telecommunication lines in the 
external telecommunications cable are connected to service lines leading 
into a facility (station protectors) and/or on protector panels within the 
facility where service lines are connected to lines leading to the 
telecommunications equipment (plug-in protectors). 
Conventional station protectors include a housing having two depending 
terminals, connected to respective ones of the telecommunication and 
service lines being bridged. A ground terminal also depends from the 
housing and is connected to a line leading to ground. Within the housing 
are a pair of bulky copper busses fastened to the housing by retainers. 
Each buss is electrically connected to one of the two terminals. A ground 
buss is disposed in the housing and is electrically connected to the 
ground terminal. The ground buss underlies the other two busses but is 
electrically isolated from them by spacers formed of dielectric material. 
Bridging the two busses is an overload detector in the form of a gas tube. 
The overload detector is also electrically connected to the ground buss. 
During normal operating conditions, the overload detector electrically 
connects the two busses while isolating the two busses from the ground 
buss. When an overload condition occurs, the overload detector connects 
the two busses to the ground buss and hence, to the ground terminal. If 
the overload condition passes, the overload detector resumes the 
electrical connection between the two busses isolating them from the 
ground buss. If the overload condition persists or is severe such that the 
current through the station protector exceeds the rating of the overload 
detector, the dielectric spacers vaporize establishing a permanent 
electrical connection between at least one of the two busses and the 
ground buss. 
Although these protectors work satisfactorily, they are difficult to 
assemble resulting in increased assembly time and worker frustration. This 
translates directly into increased labour costs. Conventional plug-in type 
protectors operate in a similar manner and suffer from the same 
disadvantages. Accordingly improved protector designs are continually 
being sought. 
It is therefore an object of the present invention to provide a novel 
protector for use in a telecommunications system. 
SUMMARY OF THE INVENTION 
According to one aspect of the present invention there is provided a 
protector to interconnect a pair of telecommunications lines in a 
telecommunications system comprising: 
a base; 
at least two terminals extending from one surface of said base, each of 
said terminals to be connected to a respective one of said 
telecommunications lines; 
a ground terminal extending from said one surface to be connected to 
electrical ground; 
a printed circuit board mounted on another surface of said base and having 
electrical paths leading to said at least two terminals and to said ground 
terminal; and 
an overload detector establishing an electrical connection between said at 
least two terminals via said electrical paths in normal operation and 
establishing an electrical connection between at least one of said at 
least two terminals and said ground terminal via said electrical paths in 
the event of an overload condition. 
In the preferred embodiment, the overload detector is either in the form of 
a gas tube or an integrated circuit and establishes an electrical 
connection between the ground terminal and both of the at least two 
terminals in the event of an overload condition. It is also preferred that 
the protector further includes a fail short to establish a permanent 
electrical connection between at least one of the at least two terminals 
and the ground terminal if the overload condition exceeds the rating of 
the overload detector. 
In one embodiment, the protector includes a plurality of connectors 
extending from the circuit board, each being electrically connected to one 
of the electrical paths. The connectors receive the electrical terminals 
of the overload detector. Preferably, the connectors are in the form of 
cylindrical tubes. In this embodiment, the fail short is in the form of a 
conductor wound around one of the tubes and has opposed free ends 
extending to the other tubes. The free ends of the conductor are isolated 
from the other tubes by insulating material designed to vaporize in the 
event of a severe overload condition so that the fail short connects 
electrically the three tubes. 
According to another aspect of the present invention there is provided a 
method of assembling a protector to interconnect a pair of 
telecommunication lines in a telecommunication system, said protector 
including a base from which at least two terminals and a ground terminal 
depend and an overload detector to establish an electrical connection 
between said at least two terminals in normal operation and to establish 
an electrical connection between at least one of said at least two 
terminals and said ground terminal in the event of an overload condition, 
said method comprising the steps of: 
mounting a printed circuit board having electrical traces thereon on said 
base; and 
electrically connecting said traces to said at least two terminals and to 
said ground terminal as well as to said overload detector. 
The present invention provides advantages in that the protector can be 
manufactured and assembled in a much faster and easier manner than prior 
art protectors. This reduces worker frustration and decreases labour costs 
.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 1 to 4, a protector for use in a telecommunications 
system to establish an electrical connection between two lines is shown 
and is generally indicated to by reference numeral 10. In this particular 
example, the protector is in the form of a station protector to 
interconnect a telecommunications line in an external telecommunications 
cable to a service line extending to a facility. As can be seen, the 
station protector 10 includes an enclosed, generally rectangular housing 
12 having a base 14, upright walls 16 about the periphery of the base 14 
and a top 17. The top 17 is removable to expose the interior of the 
housing 12. A pair of line terminals 18 and 20 depend from opposed ends of 
the base 14. One of the terminals 18 is to be connected to the 
telecommunications line while the other terminal 20 is to be connected to 
the service line. A ground terminal 22 is also secured to the base 12 
midway between the terminals 18 and 20 and extends to one side of the 
housing 12. The ground terminal 22 is to be connected to a ground post 
leading to electrical ground. 
Surface mounted on the base 14 within the housing 12 is a printed circuit 
board 30 (best seen in FIGS. 2 and 4). The printed circuit board is 
secured to the base 14 by a plurality of fasteners 32 passing through 
apertures 33 provided in the printed circuit board 20. Three copper traces 
34, 36 and 38, each defining an electrical path are on the printed circuit 
board. Copper trace 34 has one end electrically connected to the terminal 
18 by way of one of the fasteners 32 and another end electrically 
connected to an upright metal tubular connector 40. Similarly, copper 
trace 36 has one end electrically connected to the terminal 20 by way of 
another of the fasteners 32 and another end electrically connected to an 
upright metal tubular connector 42. Copper trace 36 has one end 
electrically connected to the ground terminal 22 by way of yet another 
fastener 32 and another end electrically connected to a third upright 
metal tubular connector 44 positioned between connectors 40 and 42. The 
three connectors are accommodated by apertures 46 provided in the printed 
circuit board 30 and are arranged in a row. The connectors accommodate the 
pins 50 of an integrated circuit overload protector 52 such as that 
manufactured by Teccor of Texas under part number P152C. 
A fail short 54 is associated with the tubular connectors 40, 42 and 44 and 
is in the form of a conductor wound around the central tubular connector 
44. The two free ends of the fail short 54 are positioned adjacent the 
connectors 40 and 42 and are covered by insulating material 56 to isolate 
electrically the fail short 54 and the connectors 42 and 44. 
The operation of the station protector 10 will now be described. During 
normal operating conditions, the overload detector 52 electrically 
connects the terminals 18 and 20 by establishing an electrical connection 
between copper traces 34 and 36 while isolating the terminals from the 
ground terminal 22. When an overload condition occurs, the overload 
detector 52 connects the terminals 18 and 20 to the ground terminal 22 by 
establishing an electrical connection between copper trace 38 and copper 
traces 34 and 36. If the overload condition passes, the overload detector 
52 resumes the electrical connection between the terminals 18 and 20 while 
isolating them from the ground terminal 22. If the overload condition 
persists or is severe such that the current through the station protector 
10 exceeds the rating of the overload detector 52, the insulating material 
56 covering the free ends of the fail short 54 vaporizes establishing a 
permanent electrical connection between connectors 40, 42 and 44 and 
hence, between the terminals 18 and 20 and the ground terminal 22. In this 
case, the station protector 10 must be replaced in order to reestablish 
the desired connection between the telecommunication and service lines. 
During manufacture of the station protector 10, the connectors 40 to 44 are 
inserted into the apertures 46 formed in the printed circuit board 30 and 
are soldered in place to connect them electrically to the copper traces 34 
to 38. The fail short 54 is then wound about the connector 44 and 
positioned to contact connectors 42 and 44. The pins 50 of the overload 
protector 52 are then inserted into the connectors and soldered. With the 
printed circuit board 30 assembled in this manner, it can be placed in the 
housing 12 and secured to the base 14 by the fasteners 32, allowing the 
protector 10 to be assembled quickly and with ease. If desired, the 
overload protector 52 can be soldered to the connectors 40 to 44 after the 
printed circuit board 30 has been placed in the housing and secured to the 
base by the fasteners. 
Referring now to FIGS. 5 to 7, another embodiment of a protector is shown 
and is generally indicated to by reference numeral 110. In this embodiment 
like reference numerals will be used to indicate like components of the 
previous embodiment with a "100" added for clarity. The protector 110 is 
of the plug-in type and is designed to plug into a terminal panel such as 
that disclosed in U.S. Pat. No. 5,044,962 issued on Sep. 3, 1991 and 
assigned to the assignee of the present application, to establish an 
electrical connection between telecommunications equipment in a facility 
and a service line. The plug-in protector 110 includes a base 114 formed 
of insulating material. Depending from the base are a plurality of 
terminal pins 115. 
Surface mounted on the base 114 is a printed circuit board 130. The printed 
circuit board is retained by studs 131 on the base which pass through 
apertures 133 provided in the printed circuit board. The printed circuit 
board 130 includes three copper traces 134, 136 and 138, each defining an 
electrical path. Copper trace 134 electrically connects two of the 
terminal pins to an upright metal tubular connector 140. Similarly, copper 
trace 136 electrically connects two of the terminal pins to an upright 
metal tubular connector 142 while copper trace electrically connects a 
ground terminal pin to a third upright metal tubular connector 144 
positioned between connectors 140 and 142. The three connectors are 
received in apertures 146 provided in the printed circuit board 130 and 
are arranged in a row. A gas tube overload protector 152 such as that 
manufactured by Joslyn of California under part number 2026-35-C2 includes 
a pair of wire terminals which are accommodated by the connectors 140 and 
142. The third terminal of the overload detector 152 is in the form of a 
metal ring centrally positioned between the wire terminals and contacts 
the connector 144. 
A fail short 154 is associated with the tubular connectors. The fail short 
is in the form of a conductor wound around the central tubular connector 
144. The two free ends of the fail short 154 contact a respective one of 
the two connectors 140 and 142 respectively. Unlike the previous 
embodiment, the ends of the fail short 154 are electrically isolated from 
the connectors 140 and 142 by insulating material 156 surrounding the 
connectors. As one of skill in the art will appreciate, the protector 110 
is also easily assembled. 
The present invention provides advantages in, that the design of the 
protectors allows them to be manufactured quickly and easily as compared 
to prior art designs. This of course allows production to be increased 
while reducing labour costs. 
Although the station protector has been shown to accommodate an integrated 
circuit overload protector while plug-in protector has been shown to 
accommodate a gas tube overload detector, it should be realized that each 
protector can accommodate other types of overload protectors. It should 
also be appreciated by those of skill in the art that variations and 
modifications may be made to the present invention without departing from 
the spirit and scope thereof as defined by the appended claims.