Telephonic communications – Diagnostic testing – malfunction indication – or electrical... – Of trunk or long line
Reexamination Certificate
2000-10-17
2003-09-02
Nguyen, Duc (Department: 2643)
Telephonic communications
Diagnostic testing, malfunction indication, or electrical...
Of trunk or long line
C379S021000, C379S029010
Reexamination Certificate
active
06614881
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to telecommunications and, more particularly, to telecommunication conductor test circuits and methods for using such telecommunication conductor test circuits.
BACKGROUND OF THE INVENTION
Network Interface Devices (NIDs) are used by telecommunications companies to connect connector wires of a multi-core cable to service wires that extend to customer residences or places of business. Such NIDs are typically mounted outdoors at a customer residence or place of business. The telecommunications company multi-core cable typically extends from a switching center commonly referred to as a central office (CO) to provide communications service to one or more neighborhoods including a plurality of customers. Thus, once a pair of wires, typically referred to as tip and ring lines, from the multi-core cable are connected to a customer's service wires, a connection is provided between the customer and the CO as will now be described.
Referring to the schematic illustration of
FIG. 1
, a typical telephone company (Telco) telecommunications multi-conductor cable
20
extends from the Telco central office (CO)
22
to feed pedestals in a neighborhood or neighborhoods. The Telco telecommunications conductor cable
20
may include 900 or more pairs of telecommunications conductor wires. At a splice
24
, one or more of the pairs of telecommunications wires are accessed.
FIG. 1
illustrates a single pair including a tip conductor
26
and ring conductor
28
which are spliced at the splice
24
into a cable extending to pedestal
32
. Note that, while only one pair of wires
26
,
28
is illustrated, the splice typically includes bridge connections for 25 pairs of wires with a 25 pair cable
30
extending from the splice
24
to the pedestal
32
.
In the pedestal
32
, the telecommunications wire pair
26
,
28
is connected to a terminal block
34
. It is further to be understood that, while only one terminal block
34
is illustrated, a terminal block assembly including a plurality of module stations, which may share a common base, is typically provided for all the pairs of the cable
30
. The terminal block
34
provides a connection point between telecommunications wire pair
26
,
28
and the customer service wires
36
. A telecommunications connection may thus be provided between the customer
38
and the Telco central office
22
.
As is further shown in the illustration of
FIG. 1
, an additional demarcation point between incoming telephone company lines and customer service wires is provided by the NID
40
which may be mounted on the premises of the customer
38
. The NID
40
typically includes one or more terminal connection devices which are also typically referred to as network interface devices. The connector device in the NID
40
typically includes a removable jumper cable allowing convenient breaking of the connection between the customer service wires inside the premises of the customer
38
and the telephone company side of the telecommunications infrastructure. The removable jumper demarcation may use an RJ-type connector which may further provide a test port isolating customer wires from the telephone company wires. Such devices are illustrated, for example, in U.S. Pat. No. 4,945,559.
The telecommunications infrastructure as described with reference to
FIG. 1
is generally directed to providing conventional voice services to a plurality of customers
38
. The conductors
20
,
26
,
28
,
36
are typically copper wires well suited to supporting voice communications. With the increased popularity of data based communications, which are typically digital transmissions, additional demands are being placed on the telephone infrastructure. For example, the Internet is growing increasingly popular with expanding information and services available to customers utilizing the Internet. The increase in content and opportunity for utilization of the Internet further may make it desirable to provide increasing data rates for communications over the telephone infrastructure.
While conventional modems designed for use over the telephone infrastructure are suited to the systems described with reference to
FIG. 1
, they are typically limited in their communication rate, for example, to 56 kilo bits per second (kbps). More recently, the digital subscriber line (DSL), very high data rate DSL (VDSL), asymmetrical DSL (ADSL) and other DSL technologies have been proposed for bringing higher band width information communications to homes and small businesses over ordinary copper telephone lines such as the cable infrastructure illustrated in FIG.
1
. The DSL approach is intended to provide downstream communications connections at data rates from approximately 1.544 megabits per second (mbps) through 384 kbps. However, the data rate available for any individual customer
38
may depend upon a variety of characteristics of the Telco infrastructure including the distance between the customer
38
and the Telco central office
22
.
The conductor wire pairs utilized for providing either analog and/or digital services between a customer
38
and the Telco central office
22
are typically tested to insure that they are of sufficient quality to provide the desired services. For example, one known approach for testing at a demarcation point of a customer premises, such as the NID
40
, is the use of the maintenance termination unit (MTU). One known type of MTU is typically referred to as a half ringer. A half ringer places a resistor and a capacitor in series across the incoming telecommunications wire pair at the demarcation point to the customer premises. A typical half ringer will utilize a 470 kilo-ohm (k&OHgr;) resistor in series with a one micro farad (&mgr;F) capacitor. The presence of the MTU may be remotely detected from the telephone company's central office. Accordingly, when a customer complaint is received, an individual customer wire pair can be tested remotely and the telephone company may be able to determine if the wiring problem is on the customer's wires or the telephone company's wires without the necessity of dispatching a service truck to the customer premises.
The MTU may be detected when the customer wires are disconnected at the test point, for example, by applying a voltage and detecting the current flow through the MTU circuit. An alternating current signal is utilized to detect the circuit as, under normal DC line conditions, no current flows through the MTU, thus avoiding unnecessary current flows through the MTU when it is not in use. Furthermore, as a typical customer telephone in an off hook condition appears as approximately 2 k&OHgr;, the MTU, during transmission of voice signals, generally has no detectable impact on the perceived quality of the phone service. However, a half ringer has a disadvantage in that, when a customer phone is off hook, the typically 2 k&OHgr; characteristic of the phone is detected rather than the MTU. Such MTUs may further provide an undesirable degradation in the performance characteristics of the wire pair under high frequency signal transmission conditions, such as those utilized with DSL service. An example of such an MTU is described generally in U.S. Pat. No. 4,309,578.
A further approach to providing an MTU includes the use of a solid state thyristor (or triac) in line for one of the wire pair, typically the ring line. The gate of the thyristor is coupled back to the ring input, typically through a 20 volt zener diode. Thus, when a line voltage of greater than about 20 volts is presented across the wire pair, the thyristor is activated and the circuit is active for phone service. During test conditions, the test circuit may be presented with a lower voltage, such as 10 volts, across the wire pair which does not turn on the thyristor (or triac) and thereby, essentially, disconnects the customer phone. Current flow may then be monitored and if current flows at a low (e.g., 10 volt) condition, this may be understood to indicate a short or other defec
Myers Bigel & Sibley & Sajovec
Nguyen Duc
Tyco Electronics Corporation
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