Abstract:
A digital telephone switch allows transparent switching from a convention telephone service to a cable digital telephone service. The switch is connected to the customer premises equipment and to the old and new telephone services. In its initial state, the switch connects the customer premises equipment to the old telephone service, leaving the new telephone service disconnected. Once a ring is detected on the new telephone service, or another appropriate control signal is received, the switch disconnects the customer premises equipment from the old telephone service and connects the customer premises equipment to the new telephone service. One embodiment can switch back and forth between the old and new telephone services to accommodate intercoms and the like.

Description:
REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of U.S. Provisional Patent Application No. 60/671,490, filed Apr. 15, 2005, whose disclosure is hereby incorporated by reference in its entirety into the present disclosure. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to a digital telephone switch and more particularly to a switch which allows a smooth and automatic switchover from an Incumbent Local Telephony Provider provided telephony service (ILEC) to a Multiple Service Operator (MSO) provided service. Further, in some applications the switchover could be made back and forth between the ILEC service and the MSO service. Further, in some applications the switchover could be made back and forth between another telephony service (eg. non-subscriber loop (NSL) based) and the MSO service. 
     DESCRIPTION OF RELATED ART 
     Cable television companies (MSOs), seeking to compete for telephone customers with incumbent local telephone companies, are marketing digital cable telephone services. As a result of the Telecommunications Act of 1996, consumers who choose to purchase MSO provided telephony services have the right to maintain their incumbent telephone number. In this case, the ILEC is required to transfer the phone number to the MSO. This process is referred to as Local Number Portability, and the ILECs are required by law to port the consumer&#39;s number to the MSO within a set time period; however the time can vary for any given port. In a typical cable telephone installation, a multimedia terminal adapter (MTA) is installed at the customer&#39;s premises to provide an interface between the cable network and the customer&#39;s telephony wiring. 
     The MTA must be installed at the customer&#39;s premise, connected to the cable network and connected to the customer&#39;s telephony wiring. Further, the ILEC must be disconnected from customer premise telephony wiring. In order for an MSO to coordinate the hardware installation requirements with the local number portability requirement as well as ensure that the customer who is having their number ported to the MSO is never without phone service, considerable logistics are required for a cost effective installation. Installations of MSO supplied telephony services in multi-dwelling units (MDUs) provide further challenges. In many cases, MDUs are provisioned with Non Subscriber Loop (NSL) switched based intercom systems that provide connectivity between a front lobby telephone and a telephone in a given apartment unit in the MDU. In traditional NSL based applications, in order to accommodate this type of connectivity, an NSL switch switches the front lobby phone onto the given apartment&#39;s telephony wiring and at the same time switches the ILEC&#39;s telephony service off of the telephony wiring of the same apartment. Once the front lobby interaction is complete, the front lobby phone is switched off of the apartment&#39;s telephony wiring, and the ILEC telephony service is switched back on to it. Hence, the NSL Intercom switch has a dedicated input connection from the ILEC provided telephony service for each apartment in the MDU and an input from the front lobby telephone(s). There is an NSL output for each apartment in the MDU and these are directly connected to the telephony wiring of the respective apartments. The NSL is typically located close to the incoming ILEC telephony wiring, which typically enters an MDU in a single centralized location (eg. Basement). 
     MSOs provide telephony service by installing an MTA in the apartment. Hence, the telephony service provided by an MSO within an MDU is distributed. In order for an MSO to install their telephony service and accommodate an NSL Intercom solution they would have to disconnect the ILEC service at the input of the NSL switch, “back feed” the MTA&#39;s telephony output out of the apartment and connect it to the input of NSL unit. Typically, it is very time consuming for the MSO&#39;s technician to find the suitable connections in order to implement the “back feeding” process. 
     SUMMARY OF THE INVENTION 
     There thus exists a need in the art to make the installation of a cable telephone system more convenient and less disruptive for the customer. 
     It is therefore an object of the invention to simplify the switch-over of the CPE from the ILEC to the MTA. 
     It is another object of the invention to reduce or even eliminate the down time during which the switch-over occurs. 
     It is still another object of the invention to provide an option to configure the CPE for connection to the MTA before the MTA is properly provisioned to operate. In this case the MTA may still need to be provisioned with the phone number that needs to be ported from the ILEC. 
     It is yet another object of the invention to provide a general solution which can be adapted to any switch-over from one telephone system to another. 
     To achieve the above and other objects, the present invention is directed to a digital telephone switch which has connection points for the CPE and first and second telephone systems (such as the ILEC and the cable telephone system via the MTA). The digital telephone switch includes a switch which, in its default state, connects the CPE to the first telephone system and leaves the CPE disconnected from the second telephone system. When the digital telephone switch detects a ring on the second telephone system, the digital telephone switch knows that the second telephone system is active. It then switches the switch to connect the CPE with the second telephone system, thereby disconnecting the CPE from the first telephone system. 
     The switch can have a reset feature to reset the switch to its original position. Such a reset feature should be difficult to actuate accidentally. In one example of such a reset feature, a 9V battery is connected between two reset terminals. 
     The digital telephone switch is used as follows. The switch is connected between the CPE and the ILEC at any time before the switch-over. When the MTA is installed at the customer&#39;s premises, the MTA is connected to the appropriate port. When the MTA is activated, the first incoming call causes a ring signal to be applied to the digital telephone switch, at which time the digital telephone switch flips the switch to connect the CPE with the MTA. The ILEC is then disconnected. 
     The present invention offers the following advantages. A single-shot switch, triggered by the initial ring of the MTA, switches the customer&#39;s telephone service from the ILEC to the MTA. The switch allows an operator to install the CPE without having to coordinate the installation with the back office staff, thereby allowing the MTA to be installed at a later date. The switch minimizes the likelihood of false triggering by noise picked up on UTP (unshielded twisted pair) wiring. The switch can be provided in various form factors, including a wall or table mount unit provisioned with RJ 11 ports, and outdoor unit provisioned with IDC connectors or in a wall plate format provisioned with appropriately configured RJ 11 ports and wire connection point terminals. A preferred embodiment has standard RJ11 jacks for connection to the CPE, the ILEC, and the MTA. In embodiments having the reset functionality, that functionality allows redeployment of the switch to other locations once the switch has outlived its usefulness at a single location. 
     By installing a switch device that can automatically and simultaneously switch in the MSO provided phone service/switch out the ILEC service to/from the customer premise telephony wiring once the porting process is completed, considerable operational efficiencies (and hence economic savings) can be achieved. Further, it is ensured that the customer never experiences a disruption in their telephony service. 
     Another embodiment allows back-and-forth switching between the ILEC and the MTA. Such an embodiment would be useful in multidwelling units (MDUs) which are configured with NSL based intercom systems. NSL systems are designed to work in conjunction with ILEC telephony service and switch the apartment premise wiring between the ILEC telephone service and the front lobby telephone service on an as required basis. Typically, the ILEC service and the front lobby phone service are connected to the input side of the NSL device (generally located in the MDU basement, where each ILEC service for each apartment enters the MDU) and the output side of the NSL feeds the apartments (generally through riser cables) in the MDUs. In the case of the MSO, accommodating NSL intercom functionality to the apartment becomes difficult due to the fact that in the case of the MSO provided phone service, the service is provided into the apartment by means of an MTA (multimedia terminal adapter) that is itself located in the apartment. In order to accommodate NSL type functionality the MSO phone service must replace the corresponding ILEC phone service at the input of the NSL device. Since these devices are generally not located in the same location, the MSO must back feed the MTA output from the apartment to the front of the NSL device. This would typically involve finding an unused twisted pair in the riser cable (bundle of twisted pairs) so that the MTA output could be connected to it. This can be very time consuming and uneconomical. 
     To reduce the inefficiencies and economic hardship required by MSOs in order to provide their telephony service as well as accommodate NSL intercom functionality to all telephones in the apartment, the “intercom” embodiment, which allows back-and-forth switching between the NSL ILEC/Intercom telephone service and the MTA telephone service, can be used. When a user&#39;s telephone is connected to the MTA and a call over the ILEC/Intercom line is detected, the “intercom” embodiment switches the user&#39;s telephone equipment back to the ILEC/Intercom line to allow the apartment user to address the call from the front lobby. Once the switch detects that either the user or the visitor has hung up, the switch switches the user&#39;s telephone equipment back to the MTA. 
     If the call over the ILEC/Intercom line is detected while the user is on an MTA call, the switch generates a call-waiting beep to allow the user to take the ILEC/Intercom call. During the ILEC/Intercom call, the impedance of the connection to the MTA is maintained such that the MTA call is kept on hold rather than disconnected. 
     Also, when the switch according to the second preferred “intercom” embodiment detects that the power to the MTA has been lost or the MTA has been disconnected, the switch switches the user&#39;s telephone equipment back to the ILEC. Thus, the switch can easily accommodate power failures and the like. 
     If a switch device is placed in the apartment that will switch the connection of the apartment&#39;s telephony wiring between the incoming NSL based telephony signals and the MSO provided telephony signal, the “back feed” requirement can be eliminated, and operational efficiencies can be maintained. In order to ensure that the apartment is always provisioned with telephony service provided by the MSO, this switch must ensure that the apartment telephony wiring is always connected to the MSO provided service as a default. The only time the switch connects the NSL provided service to the apartment wiring is when a) the NSL service is ringing and the apartment telephone is on the hook or b) the apartment resident decides to “flash” over to the NSL service while on a call through the MSO provided service. 
     If the MTA power is removed and/or the MTA connection to the device is removed, the Intercom unit will switch back to the Telco/Intercom side. However, if the MTA power is restored or the MTA is plugged back into the MTA port on the Intercom device, it will switch back to the MTA service. Thus, in apartments where there is a high turnover rate of tenants, phone service can easily be provided from the ILEC or the MSO. When a tenant moves out, that tenant can take the MTA device out of the apartment, and the Intercom unit will switch back to the Telco/Intercom side. The next tenant can move in and either obtain phone service from the ILEC without the ILEC having to roll a truck or obtain MSO Digital Voice Service by plugging a new MTA into the MTA port of the Intercom unit. The MSO can thus save money by accommodating customer self installation of the MTA. 
     The present invention, including both preferred embodiments, offers an advantage in accommodating local number portability (LNP). Once a user&#39;s telephone number is transferred from the ILEC to the new telephone service, telephone calls start to come in over the MTA rather than the ILEC, thereby triggering the switch. Accordingly, the user does not have to remember when the number transfer is supposed to take place in order to disconnect and reconnect telephone equipment; instead, the transition happens transparently to the user. 
     Modifications of either or both of the preferred embodiments are possible. An outdoor version of either embodiment can be implemented, with a hardened design that allows installation in a telephone company&#39;s NID (network interface device), a CATV enclosure, or a stand-alone installation. Of course, the connectors on the unit can be adapted accordingly. Either of the embodiments can be incorporated into a wall plate to allow cleanliness of installation; that modification is basically concerned with different packaging. A switch can switch back and forth between the ILEC (incumbent local exchange carrier) and the MTA according to whether the incoming ring signal is from the MTA side or the ILEC side. Such a switch can be further modified such that the operator can remotely lock the switch position to the MTA position. Remote control can be performed by tone recognition (for example, a caller can enter a specific sequence of numbers), by caller ID, or a combination of the two. 
     The switch does not even have to be a separate unit at all. It can be incorporated into an MTA or a cable modem. For example, a manufacturer of cable modems that produces a cable modem with an EMTA (embedded MTA) can also embed the switch into the cable modem. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Two preferred embodiments of the present invention will be set forth in detail with reference to the drawings, in which: 
         FIG. 1  is an external view showing the digital telephone switch of the first preferred embodiment; 
         FIG. 2  is a functional schematic diagram showing the switching configuration of the digital telephone switch of the first preferred embodiment; 
         FIG. 3  is a functional schematic diagram showing the cross connect requirements at the telephone company demarcation point according to the first preferred embodiment; 
         FIG. 4  is a flow chart showing a method in which the digital telephone switch of  FIGS. 1 and 2  is installed and used; 
         FIG. 5  is a circuit diagram showing a construction of the digital telephone switch of  FIGS. 1 and 2 ; 
         FIG. 6  is a circuit diagram showing a construction of the control block of  FIG. 5 ; 
         FIG. 6A  is a circuit diagram showing an alternative relay which may be used in the control block of  FIG. 6 ; 
         FIG. 7  is a schematic diagram showing an overview of the digital telephone switch according to the second preferred embodiment; 
         FIG. 8  is a wiring diagram showing connections from three internal connectors in the digital telephone switch of  FIG. 7 ; 
         FIGS. 9-13  are circuit diagrams showing various sections of the digital telephone switch of  FIG. 7 ; and 
         FIG. 14  is a high-level block diagram showing a multimedia terminal adapter or embedded multimedia terminal adapter in which the switch of either of the preferred embodiments is embedded. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Two preferred embodiments will be described in detail with reference to the drawings, in which like reference numerals refer to like elements throughout. 
       FIG. 1  is an external view of the digital telephone switch  100  according to the first preferred embodiment. The digital telephone switch  100  has a case  102  with a port  104  for a telephone, a port  106  to be connected to both the ILEC and the CPE (customer premises equipment) in a manner to be explained below, and a port  108  for the MTA. The ports  104 ,  106  and  108  are configured as standard RJ11 jacks. However, other connections could be used as needed. For example, in an outdoor unit for installation in a NID or the like, IDC type connections could be used. Similarly, in a unit configured as a wall plate, a combination of RJ11 and IDC or wire terminal type connections could be used. An LED  110  indicates the status of the digital telephone switch  100  in a manner to be explained below. 
       FIG. 2  shows a functional schematic diagram of the digital telephone switch  100 . It is well known in the art that a standard telephone interface includes up to four lines, which are color coded black, read, green and yellow. The port  104  includes a black line  202 , a red line  204 , a green line  206 , and a yellow line  208 . The port  106  includes a black line  212 , a red line  214 , a green line  216 , and a yellow line  218 . The port  108  includes a black line  222 , a red line  224 , a green line  226 , and a yellow line  228 . The read and green lines  204 ,  206  of the port  104  are connected to the red and green lines  214 ,  216  of the port  106 . 
     A switching element  232  selectively connects the red line  214  of the port  106  to either the black line  212  of the port  106  or the red line  224  of the port  108 . A switching element  234  selectively connects the green line of the port  106  to either the yellow line  218  of the port  106  or the green line of the port  108 . The switching elements can be implemented in any suitable way, e.g., mechanical switches. 
     The ports  104 ,  106  and  108  are connected as follows. For the port  104 , the red and green lines  204 ,  206  are connected to the ring and tip lines, respectively, of a local telephone  240 . The black and yellow lines  202 ,  208  are normally unconnected, but can be connected to a nine-volt battery  242  to reset the digital telephone switch  100 . For the port  106 , the black and yellow lines  212 ,  218  are connected to an ILEC cross connection  246 , which will be explained below with reference to  FIG. 3 . The read and green lines  224 ,  226  are connected to customer premises wiring  248 . For the port  108 , the read and green lines  224 ,  226  are connected to an MTA cable modem  250 , while the black and yellow lines  222 ,  228  are unconnected. 
     The switching elements  232  and  234 , in their default positions, connect the red lines  204 ,  214  to the black line  212  and the green lines  206 ,  216  to the yellow line  218 , thus connecting the local telephone  240  and the customer premises wiring  248  to the ILEC cross connection  246 . When switched over, the switching elements connect the red lines  204 ,  214  to the red line  224  and the green lines  206 ,  216  to the green line  226 , thus connecting the local telephone  240  and the customer premises wiring  248  to the MTA cable modem  250 . 
     The ILEC cross connection  246  has the configuration shown in  FIG. 3 . The incoming ILEC line  302  includes a black line  312 , a red line  314 , a green line  316  and a yellow line  318 , while the outgoing cross-connected line  322  includes a black line  332 , a red line  334 , a green line  336  and a yellow line  338 . In the incoming ILEC line  302 , the red and green lines  314 ,  316  are used as a ring line and a tip line, respectively, while the black and yellow lines  312  and  318  are not connected. In the cross connection  246 , the red and green lines  314  and  316  are connected to the black and yellow lines  332  and  338  of the outgoing cross-connected line  322 , while the red and green lines  334 ,  336  of the cross-connected line  322  are unconnected. 
     The digital telephone switch  100  is connected in the following manner, as shown in the flow chart of  FIG. 4 . 
     Step  402 . Cross-connect the wiring at the telephone company demarcation point, i.e., the point where the ILEC wiring enters the customer&#39;s premises. That is done as explained above with reference to  FIG. 3 . 
     Step  404 . Connect the port  106  of the digital telephone switch  100  to customer premise wiring  248 . That may be done with any RJ11 jack in the customer premises. However, it must be done with a UTP cable which is four-wire and not cross-connected, so that both the ILEC cross connection  246  and the customer premises wiring  248  are connected. 
     Step  406 . Ensure that the digital telephone switch is reset. If the digital telephone switch needs to be reset, see step  416  below. 
     Step  408 . Connect the output of the MTA  250  to the port  108  on the digital telephone switch. The UTP wiring need not be four-wire, but it must not be cross-connected. 
     Step  410 . Ensure that the MTA is powered. That is done in accordance with the instructions for the MTA, not for the digital telephone switch. 
     Step  412 . After approximately 30 seconds, the LED  110  starts to flash, indicating that the MTA  250  is connected and that the digital telephone switch  100  is ready for operation. Of course, that time period is a matter of design choice. 
     Step  414 . If desired, connect a telephone to the port  104  of the digital telephone switch  100 . 
     Step  416 . If it is, or ever becomes, necessary to reset the digital telephone switch  100 , apply a nine-volt battery or other nine-volt DC source across the black and yellow lines  202 ,  208  of the port  104 . 
     When the switching elements  232 ,  234  are in their initial positions, the CPE will be connected to the POST cross connection, and the MTA will not be connected to the CPE. Once an incoming ring from the MTA is detected, the switching elements  232 ,  234  will switch over. Thus, the CPE will be disconnected from the ILEC cross connection  246  and connected to the MTA  250 . 
     An implementation of the digital telephone connector  100  of the first preferred embodiment will be explained in greater detail with reference to the circuit diagrams of  FIGS. 5 and 6 .  FIG. 5  shows the manner in which the ports  104 ,  106 ,  108  are connected to one another and to a control block  502 . As shown in  FIG. 6 , the control block  502  is configured to have a relay  602  for implementing the switching elements  232 ,  234  of  FIG. 2 , a relay power section  604  for powering the relay  602 , a ring detect section  606  for detecting a ring on the MTA, and an MTA-available flasher section  608  for actuating the LED  110 . The relay  602  may be replaced with the relay  602 A of  FIG. 6A . 
     The specifications of the digital telephone switch  100  according to the first preferred embodiment are as follows: 
     
       
         
               
               
               
             
           
               
                 TABLE I 
               
               
                   
               
               
                   
                 Parameter 
                 Specification 
               
               
                   
               
             
             
               
                   
                 Implementation 
                   
               
               
                   
                 requirements 
                   
               
               
                   
                 Cross connect at 
                 See FIG. 3 and accompanying disclosure. 
               
               
                   
                 telephone company 
                   
               
               
                   
                 demarcation 
                   
               
               
                   
                 Input 
                   
               
               
                   
                 DC line voltage 
                 22-60 V DC on red and green lines 224, 
               
               
                   
                   
                 226 of port 108 
               
               
                   
                 Startup current 
                 100 μÅ maximum 
               
               
                   
                 Power-up time 
                 2.5 minutes maximum 
               
               
                   
                 Quiescent current 
                 50 μÅ maximum 
               
               
                   
                 Operation 
                   
               
               
                   
                 MTA ring detection 
                 40 VAC to 115 VAC 
               
               
                   
                 Switch to MTA 
                 Within 0.5-2 cycles of ring tone 
               
               
                   
                 MTA in-service 
                 Flashing red LED 110 
               
               
                   
                 indication 
                   
               
               
                   
                 Switch reset 
                 9 V DC applied across black and yellow 
               
               
                   
                   
                 lines 202, 208 of port 104 
               
               
                   
                 Other 
                   
               
               
                   
                 Temperature 
                 −40° C. to +60° C. 
               
               
                   
               
             
          
         
       
     
     The digital telephone switch  100  requires thirty seconds of charge-up time off of the MTA  250  before it can become operational. As noted above, that time period is a matter of design choice. 
     A second preferred embodiment will now be set forth. As explained above, the second preferred embodiment, or the “intercom” embodiment, allows two-way switching. That is, the switch according to the second preferred embodiment switches back to the ILEC line when a ring is detected on the ILEC line or when the switch detects that the MTA has lost power or is otherwise unavailable. The second preferred embodiment is based on the first preferred embodiment. Therefore, the disclosure relating to the first preferred embodiment applies with equal force to the second preferred embodiment wherever appropriate. 
       FIG. 7  shows an overview of the switch  700  according to the second preferred embodiment. For simplicity, only the ports  104 ,  106 ,  108  are shown. As shown, there is a hard-wired connection between the green and red lines of the ports  104  and  106 . The remaining lines are identified by the signals which they carry, which show the interconnection of the various elements shown in  FIGS. 7-13 . Similarly,  FIG. 8  shows three internal connectors J 3   802 , J 4   804 , and J 5   806 , with the lines identified by the signals which they carry, except for those lines which are unused or connected to ground  808 . 
     The circuitry for the operation of the switch  700  will be disclosed with reference to  FIGS. 9-13 .  FIG. 9  shows the MTA/relay power section  902 , with the relay  904 , and the MTA ring detect section  906 .  FIG. 10  shows the ILEC/intercom power section  1002  and the ILEC/intercom ring detection section  1004 .  FIG. 11  shows the MTA control section  1102 , again with the relay  904 .  FIG. 12  shows the microcontroller  1202  and associated circuitry  1204 .  FIG. 13  shows the ILEC off hook detection section  1302 , the ILEC ring detection circuit  1304 , and the MTA ring detection circuit  1306 . 
     As noted above, either of the two preferred embodiments can be integrated into an MTA/eMTA (enhanced MTA). An example is shown in  FIG. 14 , although other implementations can be realized instead. As shown, an MTA/eMTA  1400  includes traditional MTA/eMTA electronics  1402  with a line 1 telephone interface  1404 , a line 2 telephone interface  1406 , a 10/100 Base T interface  1408  and an RF interface  1410 . The line 1 telephone interface  1404  is connected via a switch  1412 , like any of the variations described above, to incoming ILEC telephone service wiring  1414  and outgoing premises wiring  1416 . The line 2 telephone interface  1406  is connected to an RJ 11 jack  1418 . The 10/100 Base T interface is connected to an RJ 45 jack  1420 . The RF interface is connected to a coaxial cable connection (F connector)  1422 . 
     More generally, an MTA/eMTA with an integrated telephone switch would include the following: a) a connection interface on the MTA/eMTA for the incoming ILEC telephone service; b) at least one, but maybe more, premise wiring interfaces, at least one of which would be connected to the internal switch so that either the ILEC or the MTA supplied phone service can be switched onto it; and c) a switch designed into the unit to accommodate switching the premise wiring interface between the ILEC and the MTA. In an MTA installation, it is not necessary for the switch to be triggered on the ring signal of the MTA/eMTA. Rather, it could be controlled by some other mechanism within the MTA. eg. a control signal. 
     While two preferred embodiments have been set forth in detail above, those skilled in the art who have reviewed the present disclosure will readily appreciate that other embodiments can be achieved within the scope of the present invention. For example, numerical values are illustrative rather than limiting. Also, the digital telephone switch can be reconfigured to remove the need for the ILEC cross connection by reconfiguring its internal connections, adding a port, or both. Furthermore, the digital telephone switch can operate, or be configured to operate, with any two types of telephone service, not simply the two described. Moreover, if it is not desired to connect the digital telephone switch to both the CPE and a local telephone through separate ports, the port  104  can be eliminated. Also, as noted above, the switch in either of the preferred embodiments can be controlled to switch over in response to a signal other than an incoming ring; an example of such a signal is a signal received from a remote operator over that remote operator&#39;s telephone keypad. Therefore, the present invention should be construed as limited only by the appended claims.