NZ260095A

NZ260095A - Combiner/splitter for frequency bands on telephone lines

Info

Publication number: NZ260095A
Application number: NZ26009594A
Authority: NZ
Inventors: Bruce Francis Orr
Original assignee: Alcatel Australia
Priority date: 1993-04-07
Filing date: 1994-03-15
Publication date: 1996-08-27
Also published as: AU5781394A; AU677032B2

Description

<div class="application article clearfix" id="description"> 26 0 0 9 Complete Specification Filed: | Class: Publication Date: 2..ILA!J!?...l9.9.(i.... ! V">. Journal No: A&S£l TRUE COPY NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "TV/VF SPLITTER" WE, ALCATEL AUSTRALIA LIMITED, 000 °°S A Company of the State of New South Wales, of 280 Botany Road, Alexandria, New South Wales, 2015, Australia, hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: l 260095 This invention relates to a device for use in injecting high frequency signals onto a two-wire line intended to carry low frequency signals, and to a device separating the high frequency signals from the low frequency signals. A particular application of the indention is in the transmission of television signals over telephone lines. Background of the Invention It is proposed to implement a form of cable television by transmitting television signals over subscribers' telephones lines. With modern compression and transmission techniques it is possible to transmit digital TV signals over a bandwidth of the order of 1MHz. This is, however, far In excess of the nominal frequency of a telephone line which is of the order of 10 kHz. As a result, the signals are significantly attenuated, the attenuation increasing with frequency. One technique for transmitting high rates of information is Discrete Multi-Tone (DMT). DMT involves the splitting of a bandwidth into several channels and transmitting tones in the channels to represent information. This invention serves the purpose of providing means to apply high frequency signals to a two-wire line, such as a phone line, in such c manner that normal phone signals can also be applied to the line. The invention also serves the purpose of providing means for extracting the high frequency signals from the line. Summary of the Invention 26 0 This specification discloses a signal combining device to combine a first signal having a first frequency band with a second signal having a second frequency band higher than the first frequency band into a two-wire line, the device including a first transformer having first second and third windings, the third winding being magnetically coupled to the first winding (and the second winding); the first and second windings being magnetically coupled so that a signal induced in the first winding by the third winding induces a signal in the second winding; the first and second windings being coupled in series via a first capacitor so that the signal induced in the second winding is added to the signal induced in the first winding; the distal ends of each of the first and second windings each being connected to a respective one of the wires of the two-wire line; wherein the first signal is applied across the first capacitor; the second signal is applied to the third winding; the first capacitor being substantially open circuit to the first signal and short circuit to the second signal. The specification also discloses a device for separating the signals at the receiving end. Brief Description of the Drawings Figure 1 shows an arrangement for transmitting frequency separated 26 o 0 signals over a telephone line to a subscriber, including devices at both ends emcndying the invention. Figure 2 shows an arrangement of devices for use in a telephone exchange to transmit TV signals via subscribers' lines. Figure 3A and 3B show an embodiment of the invention for extracting TV and phone signals at the subscriber' premises. Figure 4 shows an extraction device where the subscriber has extension lines. Figure 5 shows an alternative embodiment for Figure 4. Description of the Invention Figure 1 shows an arrangement for transmitting voice signals and TV signals from a central location to a subscriber over the subscriber's phone line, and for separating the signals at the subscriber's premises. The arrangement can also be used to permit the subscriber to transmit signals to the central location in a frequency band above the voice signals. This could be used, eg., to change the channel selected by the subscriber where the central location can access a plurality of such channels in response to the request signal from the subscriber. The subscriber's request could be detected by the third winding W3 of the transformer at the central location and separated from the TV signals by known means such as filters or hybrid circuits. The arrangement of Figure 1 includes at a central location such as a 26 0 0 telephone exchange a device 1 for combining voice and TV signals. The device includes a first transformer T1 consisting of windings W1, W7, and W3. Windings W1 and W2 are connected in series electrically in a high frequency path by capacitor C1. The voice signals are applied across C1 which is effectively open circuit to the voice frequencies. Optionally the voice signals are applied via a pair of windings W4, W5 which serve to block noise signals above the voice band which may interfere with the TV signals. These noise signals may be generated, eg., by the ring signal generator. The windings W1, W2 and W3 are poled as indicated so that signals induced in W2 add to signals induced in W1 across the subscriber line (L1, L2). The TV signals are applied to winding W3 and may be in the form of a plurality of tones of different frequencies spread over a bandwidth of the order of 1 MHz. A low frequency blocking capacitor C3 may be added in series with W3 to prevent voice signals being fed to the TV signal source. At the subscriber's end of the line there is a splitter 2 including a transformer consisting of windings W6, W7 and W8. W6 and W7 are again connected in a high frequency path by a capacitor C2. Voice signals are extracted across C2, and the TV signals are extracted via W8. Optionally low frequency capacitor C4 prevents voice signals appearing in the TV signal output. Figure 2 is a drawing illustrating a physical embodiment of the 26 u 0 8 combiner of Figure 1. The combiner includes a connector block 21, a plurality of signal transformers T11 to Tin, a plurality of capacitors C11 to C1n, and a plurality of blocking transformers T21 to T2n, all mounted on a PCB 22. This 5 arrangement enables n lines to carry both signals. This arrangement is designed to be mounted on the MDF (main distribution frame) of an exchange so that the combiners can be added with a minimum of change to an exchange. The n subscriber lines enter the PCB 22 from the exchange via a section of the connector block 21 and each line is 10 connected to one of the signal transformers (T11 to Tin), one of the capacitors (C11 to C1n) and one of the blocking transformers (T21 to T2n) as shown in Figure 1. The TV signals are applied to the W3 windings of ^ transformers T11 to Tin via a second portion of the connector block, and the subscriber lines are connected to a third portion of the connector block. The 15 connector block may be, eg. a Krone insulation displacement type. Figure 3A shows a splitter to be for use at the subscriber's premises. The splitter includes connector pins 31 and 32, and locking lug 33 compatible with the standard Australian telephone phone line socket so that the splitter can be plugged directly into the phone socket. The other side of the splitter 20 includes a socket (34, 35, 36) compatible with the conventional phone line plug so that the phone can be plugged into the splitter. The splitter also includes a socket 37 from which the TV signal is extracted. The socket 37 is 6 2 6 0 0 9 connected to the winding W8 (and optional capacitor C4) of Figure 1. This arrangement provides a simple plug in modification at the subscriber's premises. The TV signals may then be fed from socket 37 to an amplifier which has a gain characteristic to compensate for the frequency dependent line losses. Figure 3B shows a profile of the embodiment of Figure 3A. The embodiments of Figure 3 are suitable where the subscriber has a single phone. The embodiment of Figure 4A is suitable for the case in which the subscriber has extension phones. In this case an additional module 4 is interposed between the phone socket and the exchange line. The module 4 carries the splitter and has three pairs of terminals X1, X2; X3, X4; and X5, X6, to which are applied respectively the exchange line, the subscriber's side phone line, and the output line for the TV signals. The subscriber's side phone line is then connected to the existing plug and socket arrangement. Figure 5 shows an alternative arrangement for use where the subscriber has extension lines. In this case the module 5 is similar to the arrangement of Figure 4 but includes a first phone socket into which the first phone can be plugged directly. A phone line to the extension socket is taken off from terminals X11, X12. </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 260095 What we claim is:

1. A signal combining device to combine a first signal having a first frequency band with a second signal having a second frequency band higher than the first frequency band into a two-wire line, the device including a first transformer having first second and third windings, the third winding being magnetically coupled to the first winding (and the second winding); the first and second windings being magnetically coupled so that a signal induced in the first winding by the third winding induces a signal in the second winding; the first and second windings being coupled in series via a first capacitor so that the signal induced in the second winding is added to the signal induced in the first winding; the distal ends of each of the first and second windings each being connected to a respective one of the wires of the two-wire line; wherein the first signal is applied across the first capacitor; the second signal is applied to the third winding; the first capacitor being substantially open circuit to the first signal and short circuit to the second signal.

2. A device as claimed in claim 1 wherein the first ~i^nal is applied via high frequency choke means.

3. A device as claimed in claim 2 wherein the high frequency choke means comprises first and second coils, each connected to a corresponding 260095 side of the first capacitor.

4. A device as claimed in any one of claims 1 to 3 wherein the third winding is connected to means to extract a third signal received from the line, the third signal having a frequency band different from the first and 5 second signals.

5. A device as claimed in claim 4 wherein the extraction means comprises a hybrid circuit.

6. A device as claimed in claim 4 wherein the extraction means comprises a filter which excludes the first signal and the second signal. 10

7. A device as claimed in any one of claims 1 to 7 including a low frequency blocking capacitor in series with the third winding.

8. A printed circuit board arranged to ba mounted on an MDF of an exchange and carrying a plurality of devices as claimed in any one of claims 1 to 7 and connector means to which the exchange line, a subscriber's line, 15 and TV signal line can be connected.

9. A splitter device for separating a first signal and a second signal on a two-wire line the first signal having a frequency band lower than the band of the second signal, the device including a third transformer having sixth, seventh and eighth windings, the sixth and seventh windings being 20 connected in series in a high frequency path via a second capacitor which 2.6 0 0 9 ^ signal the first signal being taken off across the second capacitor, the second signals being taken off from the eighth winding.

10. A splitting device as claimed in claim 9 including a low frequency blocking capacitor in series with the eighth winding.

11. A splitting device as claimed in claim 9 or claim 10 including means to inject a third signal onto the two-wire line via the eighth winding, the third signal having a frequency band different from the first and second signals.

12. A splitting device as claimed in any one of claims 9 to 11 wherein the line is a telephone line and the device includes an input plug compatible with the exchange line socket and a first output socket compatible with the phone's line plug, and a third socket connected to the eighth winding via which the second signal can be extracted.

13. A splitting device as claimed in any one of claims 9 to 11 including a plurality of terminal pairs to which the exchange line, the second signal and the phone line respectively can be connected.

14. A splitting device as claimed in claim 13 including a conventional phone socket.

15. A splitter device as herein described with reference to Figures 1, 3, 4 and 5 of the accompanying drawings. ^'19 JUL 1996 * 10 2 6 0 0 9 5

16. A combiner device as herein described with reference to Figures 1 and 2 of the accompanying drawings. ALCATEL AUSTRALIA LIMITED B. O'Connor Authorized Agent P5/1/1703 </div>