The present invention relates to capacitance compensation devices for transmission lines. More particularly, the present invention relates to load coils having digital subscriber line (DSL) bypass technology for twisted pair transmission lines used in telephone service.
As the communications needs in a particular area or neighborhood change, the flexibility of the network for that area may also change. Although plain old telephone service (POTS) and DSL service are both delivered via twisted pair transmission lines, those two services have different specifications for performance. For example, distributed stray capacitance of twisted pair lines causes an insertion loss that hinders the performance of voice services. When a POTS line is over 18,000 feet in length, load coils that cancel out stray capacitance on a line must be added to the POTS line beginning at 3000 feet from the central office (CO) and repeating every 6000 feet to the customer's premises. The added load coils compensate for the distributed stray capacitance and thus, keep voice services clear across the transmission lines over long distances.
However, these added load coils also increase the insertion loss at frequencies above the voice services band. This loss is a problem for services such as asynchronous digital subscriber line (ADSL), which operates using high frequency signals. The problem is that DSL signals cannot be transmitted via transmission lines that have load coils installed because DSL signals cannot pass through a load coil. As customers move away and cancel their POTS service, the transmission line with load coils (loaded pair) becomes available. Should a new customer order DSL provisioned via the available loaded pair, a technician must cut the load coils from the loaded pair before it can be used for conveying DSL. This results in service delays and wasted labor and expenses.
It is with respect to these and other considerations that the present invention has been made.
In accordance with the present invention, the above and other problems are solved by embodiments of the present invention. Illustrative embodiments of the present invention are directed to load coils with DSL bypass technology. The present invention allows for the transmission of both digital, e.g., DSL, and analog, e.g., POTS, signals via a loaded pair. A load coil with digital signal bypass technology will block digital signals away from the load coil and pass analog signals through the load coil. The present invention addresses problems such as, but not limited to, those mentioned above by adding high and low pass filters to a base section of the standard load coil. Thus, the present invention reduces service delays, wasted labor, and expenses.
One illustrative embodiment of the present invention is an apparatus including a load coil to be placed in series with a transmission line to compensate for capacitance in the transmission line. The apparatus also includes low pass filters. One low pass filter is electrically connected in series at an inbound connection of the load coil and a second low pass filter is connected at an outbound connection of the load coil. The low pass filters are to be electrically connected in series with the transmission line to pass analog signals on the transmission line through the load coil and exclude ADSL signals on the transmission line from the load coil. Although the present and following discussion refer to ADSL signals, it should be understood that the present invention applies equally to synchronous digital subscriber lines and service as well as asynchronous digital subscriber lines and service.
The apparatus also includes a high pass filter electrically connected in parallel with a combination of the load coil in series with the low pass filters. The high pass filter is to be electrically connected in series with the transmission line to exclude the ADSL signals from the load coil.
Another illustrative embodiment of the present invention is a digital signal bypass filter in a load coil. The load coil is of the type to be spliced in series with a dual conductor transmission line to compensate for capacitance in the dual conductor transmission line for transmitting analog signals. The digital signal bypass filter includes a first capacitor electrically connected in parallel with the load coil. The first capacitor is to be electrically connected in series with a first conductor of the dual transmission line. The digital signal bypass filter also includes a second capacitor electrically connected in parallel with the load coil. The second capacitor is to be electrically connected in series with a second conductor of the dual transmission line. The first and second capacitors pass digital signals on the transmission line away from the load coil and block analog signals away from the digital signal bypass filter.
Still another illustrative embodiment of the present invention is a bypass filter connected to a load coil and an incoming and outgoing wire pair. The bypass filter includes a first inductor connected in series between a first lead of the incoming wire pair and the load coil and a second inductor connected in series between a second lead of the incoming wire pair and the load coil. The first inductor and second inductor pass an analog signal on the incoming wire pair to the load coil. The bypass filter further includes a first capacitor and a second capacitor. The first capacitor is connected in parallel with the load coil and in series between the first lead of the incoming wire pair and a first lead of the outgoing wire pair. The second capacitor is connected in parallel with the load coil and in series between the second lead of the incoming wire pair and a second lead of the outgoing wire pair.
These and various other features as well as advantages, which characterize the present invention, will be apparent from a reading of the following detailed description and a review of the associated drawings. It is intended that all such additional features and advantages be included within this description, be within the scope of the present invention and be protected by the accompanying claims.
The invention will be further understood from the following description with reference to the accompanying drawings, in which:
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
Referring to
Turning now to
In contrast, low frequencies are passed through the load coil 307 and then toward the customer premises 110. The load coil device 300 improves network flexibility because no technicians will have to dispatch to remove load coils from transmission lines conveying DSL signals. Nor will technicians dispatch to return load coils to POTS transmission lines where load coils were previously removed to carry DSL. It should be appreciated that the load coil device 300 may be a single set load coil, meaning that each load coil device is manufactured separately with its own filters. Additional details regarding the low pass and high pass filters will be described below with respect to
A high pass filter 404 is electrically connected in parallel with the combination of the load coil 307 and the low pass filters 402a and 402b. The high pass filter 404 is to be electrically connected in series with the transmission line extending between the in facilities 302 and the out facilities 304 to bypass the DSL signals around the load coil 307.
The transmission line with which the apparatus is to be used includes a pair of conductors 414 and 415. The low pass filters 402a and 402b each include an inductor 407a and 407c to be electrically connected in series with the conductor 415 of the pair, respectively at an inbound connection and an outbound connection of the load coil 307. The low pass filters 402a and 402b also respectively include second inductors 407b and 407d to be electrically connected in series with the conductor 415 of the pair, respectively at an inbound connection and an outbound connection of the load coil 307.
Additionally, the high pass filter 404 includes a first capacitor 405a electrically connected in parallel with the inductors 407a and 407c and the load coil 307. The first capacitor 405a is electrically connected in series with the conductor 415 of the transmission line. The high pass filter 404 also includes a second capacitor 405b electrically connected in parallel with the inductors 407b and 407d and the load coil 307. The second capacitor 405b is to be electrically connected in series with the conductor 414 of the transmission line.
The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.