A surge protection module which provides surge protection for at least two telecommunications lines, with some wires of each telecommunication line being protected according to a first limiting voltage, and other the wires of the telecommunications line being protected according to a second limiting voltage.

BACKGROUND OF THE INVENTION 
The present invention relates to telecommunication line surge protectors. 
More specifically, the present invention relates to a surge protector 
which provides surge protection for two telecommunications lines, wherein 
each line includes wires of at least two different maximum expected 
voltages. 
DESCRIPTION OF THE RELATED ART 
Telecommunications lines are subject to accidental electrical surges. Such 
surges are conditions of abnormally high current and/or voltage. Surges 
can be caused by lightning or short circuits. A surge can cause permanent 
damage to devices, such as telephone sets, which are connected to the 
telecommunications line. 
A typical telecommunications line includes at least two, discrete wires. 
However, many telecommunications lines contain more than two wires. For 
instance, telecommunications lines having four or eight wires are common. 
Normally, each wire of a telecommunications line will have the same, 
maximum expected voltage. The maximum expected voltage is the greatest 
voltage which is expected during operation of the telecommunications line. 
The maximum nominal voltage depends upon the telecommunications equipment 
which the telecommunications line connects. 
With respect to the maximum expected voltage, it should be noted that the 
wires of a telecommunications line are often organized into one or more 
pairs. For a pair, one wire of the pair will have voltages which approach 
the maximum expected voltage, while the other wire will be grounded and 
remain close to 0 volts. However, because of variations in the way 
telecommunications lines are connected and constructed, it is impossible 
to reliably determine which wire of a pair will bear the maximum expected 
voltage, and which wire of the pair will be grounded. For this reason, 
maximum expected voltage for surge protection purposes is the same for 
both wires of a pair. 
For instance, a first conventional telecommunications line includes two 
wires, each having a nominal expected voltage of about 200V (volts). A 
voltage of 200V is expected during a ringing operation. 
A second conventional telecommunications line includes four wires, each 
having a maximum expected voltage of about 50V. Note that both the first 
and second conventional telecommunications lines each have the same 
maximum expected voltage for each wire. 
Surge protectors for these conventional telecommunications lines should 
allow signals of the maximum expected voltage to reliably pass through the 
surge protector, while stopping signals having voltages significantly 
higher than the maximum expected voltage. For instance, for the first 
conventional telecommunications line, a surge protector which has a 
limiting voltage of 240V may be used. This allows the 200V ringing signal 
to pass (with some margin of tolerance), while stopping signals having 
more than 240V, which may cause damage to telecommunications equipment 
connected to the telecommunications line. Similarly, for the second 
conventional telecommunications line, a surge protector having a limiting 
voltage of 70V may be used. This allows the approximately 50V operating 
signals to pass (with some margin of tolerance), while stopping signals 
having more than 70V, which may cause damage to telecommunications 
equipment connected to the telecommunications line. 
However, some types of telecommunications lines have wires (or pairs of 
wires) which have more than one maximum expected voltage. While there are 
single line telecommunications surge protectors which provide different 
limiting voltages for various wires of a single telephone line, these 
protectors provide surge protection for only one telephone line. 
Therefore, a separate surge protector is required for every telephone line 
which is to be protected. A separate surge protector housing is required 
for every telecommunications line which is to be protected. Much space is 
required because there must be a separate surge protector for each 
telecommunications line. Separate installation (with its associated costs) 
are required for each telecommunications line. Importantly, each of these 
single line telecommunications surge protectors require a separate 
connection to ground, which requires separate wiring for each 
telecommunications line. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a telecommunications 
line surge protector which can be used with telecommunications lines 
including wires having more than one maximum expected voltage. It is a 
further object of the present invention to provide a telecommunications 
surge protector which will protect wires of a telecommunications line 
according to at least two different limiting voltages. It is a further 
object of the present invention to provide a telecommunications surge 
protector which can protect at least two telecommunications lines. 
According to the present invention, a telecommunications line surge 
protector includes a first input connector and first output connector, and 
a second input connector and second output connector. The first input 
connector and first output connector are connected by the first surge 
protection circuitry. The second input connector and second output 
connector are connected by the second surge protection circuitry. 
A first telecommunications line can be connected through the first input 
and output connectors, to provide surge protection for the first 
telecommunications line. The first surge protection circuitry connects the 
first input connector to the first output connector by multiple wires, 
wherein some wire(s) are protected according to a first limiting voltage 
and some wire(s) are protected according to a second limiting voltage. 
Likewise, a second telecommunications line can be connected through the 
second input and output connectors, to provide surge protection for the 
second telecommunications line. The second surge protection circuitry 
connects the first input connector to the first output connector by 
multiple wires, wherein some wire(s) are protected according to a third 
limiting voltage and some wire(s) are protected according to a fourth 
limiting voltage. 
In this way, a singe surge protector according to the present invention can 
protect two telecommunications lines. Because there are wires of two 
different limiting voltages in the first and second surge protection 
circuitry, a surge protector according to the present invention can be 
used to protect telecommunications lines which have wires subject to two 
different maximum expected voltages.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows two environments, a main building 10 and a remote building 20, 
in which surge protectors according to the present invention may be used. 
The main building 10 is a relatively large facility with many phone lines 
and a key system unit (KSU) 90. The remote building 20 is a separate 
structure, which has two remote telecommunications sets 140, 150, which 
are connected to the key system unit 90 in the main building 10. 
Telecommunications lines run from the central office to the main building 
primary protector/connector block 30. The main building primary 
protector/connector block 30 provides primary surge protection for the 
telecommunications lines at the point where the lines enter the building. 
The main building primary protector/connector block 30 is directly 
attached the building ground 40. 
Some of the telecommunications lines run from the main building primary 
protector/connector block 30, to the central office line protection module 
60. These telecommunications lines then run from the central office line 
protection module 60 to the key system unit 90 and are distributed by the 
key system unit 90 to the various telecommunications equipment (not shown) 
in the main building 10. 
The protection module 60 is a conventional telecommunication line secondary 
surge protector. Protection module 60 will protect each wire of the 
telecommunications line with the same limiting voltage. Therefore, while 
the protection module 60 can be used to protect telecommunications lines 
wherein each wire has the same maximum expected voltage, the protection 
module 60 cannot be used for telecommunications lines wherein different 
wires have different maximum expected voltages. 
The central office line protection module is detachably, mechanically 
connected to an AC surge protection module 50 by a module grounding 
connection 65. The AC surge protection module 50 is a secondary surge 
protector for AC power lines in the main building 10. 
A dual line, dual voltage telecommunications line surge protector 70a 
according to the present invention is also detachably, mechanically 
connected to the central office line protection module 60 by a module 
grounding connection 75. Two telecommunications lines run from the key 
system unit 90 to the dual line, dual voltage surge protection module 70a. 
These two telecommunications lines are station lines which are 
respectively used for the two remote telephone sets (or station sets) 140, 
150 in the remote building 20. These two telecommunications lines run from 
the dual line, dual voltage surge protection module 70a to the main 
building primary protector/connector block 30 and then to the remote 
building 20 and the two remote telephone sets 140, 150. 
The dual line, dual voltage telecommunications surge protection module 70a 
provides surge protection for two telecommunications lines, with each line 
having up to four wires. Two of these wires are protected by surge 
protection circuitry of the dual line, dual voltage surge protection 
module 70a with a limiting voltage of about 70 volts. The other two of 
these wires are protected by surge protection circuitry of the dual line, 
dual voltage surge protection module 70a with a limiting voltage of about 
240 volts. 
In this embodiment, the first remote telephone 140 set is an analog, two 
wire telephone set. The two wires have a maximum expected voltage of about 
200 volts which occurs when a ringing signal is passed on the 
telecommunications line. The dual line, dual voltage surge protection 
module 70a can be used for this line because the surge protection 
circuitry of 70a provides protection for two wires with a limiting voltage 
of about 240 volts. This allows the 200 volt ringing signal to pass 
through the surge protector, while blocking any surges which are 
significantly greater than 200 volts, thereby preventing damage to the 
remote telephone set 140. 
The second remote telephone set 150 is a four wire telephone set, where two 
of the wires have a maximum expected voltage of 200 volts for a ringing 
signal, and two of the wires have a maximum voltage of about 50 volts. The 
two 50 volt wires can be used to transmit digital signals. Because the 
dual line, dual voltage surge protection module 70a provides protection 
for two wires with a limiting voltage of 240 volts and two wires with a 
limiting voltage of 70 volts, the dual line, dual voltage surge protection 
module 70a is well-suited to provide protection to this kind of dual 
voltage line. 
Because the dual line, dual voltage surge protection module 70a is 
detachably, mechanically connected to the central office line protection 
module 60 by a module grounding connection 75, this makes it easy to add 
or remove the dual line, dual voltage surge protection module from an 
assembly of surge protection modules. Also, the dual line, dual voltage 
surge protector is grounded through the central office line protection 
module and the AC surge protection module to a common ground 80. This 
means that fewer grounding connections are necessary, because all three 
surge protection modules 70a, 60, 50 share a ground connection. 
As explained above, the station lines for the remote telephone sets 140, 
150, run from the key system unit 90, to the main building primary 
protector/connector block 30, to the remote building 20. At the remote 
building 20, the station lines are connected to a remote building primary 
protector 100. The remote building primary protector 100 provides primary 
protection for the station lines and is connected to the building ground 
110 of the remote building 20. 
The two station lines then run to the dual line, dual voltage surge 
protection module 70b in the remote building. the surge protection module 
70b is the same as the surge protection module 70a discussed above. 
Because the surge protection module 70b is a dual line protection module, 
a single module can be used for both remote telephone sets 140, 150. This 
results in an economy of space, an economy of construction materials (such 
as housings) and an economy in installation costs relative to a single 
line protection module. Furthermore, only a single connection to ground 
130 is required for two telecommunications lines. 
FIGS. 2A to 2C show three views of an embodiment of a dual line, dual 
voltage surge protection module 200 according to the present invention. 
One side of the protection module (shown in FIG. 2A) has two input 
connectors 210a, b. The input connectors are female RJ-45/11 jacks. 
RJ-45/11 jacks are standard connectors which can be used with two wire, 
four wire or eight wire telecommunications lines. Because, the present 
embodiment of the surge protection module 200 provides protection for only 
four wires (two at 70 volts limiting voltage, 2 at 240 volts limiting 
voltage, only four of the eight possible wires are active, as shown in the 
diagram of the input connector at FIG. 3. The 70 volt limiting voltage 
wires are mapped as wires 3 and 6. The 240 volt limiting voltage wires are 
mapped as wires 4 and 5. 
Alternatively, the input connector could be constructed as a four wire 
connector, as shown in FIG. 4. 
As shown in FIG. 2C, there are two output connectors 220a, b. Output 
connector 220a is connected to input connector 210a by the surge 
protection circuitry (not shown) in the surge protection module 200. 
Output connector 220b is connected to input connector 210b by the surge 
protection circuitry (not shown) in the surge protection module 200. 
The surge protection module 200 has two ears 250, 260. Each ear has two 
holes 240 for screws. These ears can be detachably, mechanically connected 
to other surge protection modules by screws (not shown). As shown in FIG. 
2A, ear 260 is offset from ear 250, so that ears of adjacent modules fit 
together and do not interfere with each other. Of course, other means of 
providing for detachable connection of the module, such as clips, are also 
possible. 
The surge protection module 200 also has a grounding strip 230. This 
grounding strip 230 runs through the module and protrudes in the vicinity 
of a screw hole 240 at each ear 250, 260. When the surge protection module 
200 is connected to other modules, the grounding strip 230 will be 
electrically connected to a similar grounding strip in the other modules, 
so that the modules will share a common ground path. 
FIG. 5 shows an embodiment of surge protection circuitry for one 
telecommunications line according to the present invention. A input 
connector 500, such as a female RJ-45/11 jack is connected to the output 
connector 520, which is also a female RJ-45/11 jack. 
Wire 3 of the input connector 500 is connected to wire 6 of the output 
connector 520, by a 6.OMEGA. (positive temperature coefficient) resistor 
P4. Wire 6 of the input connector 500 is connected to wire 3 of the output 
connector 520, by a 6.OMEGA. resistor P2. Wire 4 of the input connector 
500 is connected to wire 5 of the output connector 520, by a 20.OMEGA. 
resistor P3. Wire 5 of the input connector 500 is connected to wire 4 of 
the output connector, by a 20.OMEGA. resistor P1. 
Sidactors Q3 through Q8 are connected across the various wires and to the 
ground bus 530 as shown in FIG. 5. Sidactors Q3 and Q4 are 240 volt 
sidactors, which provide input connector wires 4 and 5 (note the wire 
numbering refers to the wire numbering of input connector 500) with a 
limiting voltage of about 240 volts. Sidactor Q5 is a 240 volt sidactor 
which controls the maximum relative voltage between wires 4 and 5. 
Sidactors Q6 and Q7 are 70 volt sidactors, which provide input connector 
wires 3 and 6 with a limiting voltage of about 70 volts. Sidactor Q8 is a 
70 volt sidactor which controls the maximum relative voltage between wires 
3 and 6. 
The surge protection circuitry shown in FIG. 5 protects different wires 
with different limiting voltages, by using sidactors of two different 
voltages (i.e., 70V and 240V). Surge protection modules according to the 
present invention, with different wires protected with different limiting 
voltages, are useful for protecting telecommunications lines wherein the 
wires have more than one maximum expected voltage, and they also can be 
useful for telecommunications line having a single maximum expected 
voltage (e.g., two wire lines). 
Although a preferred embodiment of surge protection circuitry is shown in 
FIG. 5, it should be noted that other types of surge protection circuitry 
are also possible. For example, sidactors Q5 and Q8, limiting relative 
voltage between various wires, are not absolutely necessary. 
Alternatively, surge protection can be provided by zener diodes and 
metal-oxide varistors. Fuses could also be added to the surge protection 
circuitry. 
While preferred embodiments of the present invention have been described 
above using illustrative examples, it will be understood by those skilled 
in the art that the invention is not limited by the illustrative examples 
and that various changes and modifications may be made without departing 
from the spirit or scope of the invention as set forth in the following 
claims.