Switchable POTS splitter

#The invention refers to a switchable POTS splitter within a central office for separating a voice signal from a data signal and in particular to a POTS splitter for an asymmetric digital subscriber line (ADSL) architecture.

#DSL (digital subscriber line) is a communication technology with underlies ISDN (integrated services digital network) and several variance that make up the x-DSL family of services. These include ADSL (asymmetric DSL), RADSL (rate adaptive DSL), SDSL (symmetric DSL) and VDSL (very high speed DSL).

#xDSL provides a digital connection for customers or other end users. By using signaling methods both voice and data can be transmitted over telephone lines wherein the data transmission speed is higher than with ordinary modems.

#A preferred embodiment of the switchable POTS-splitter according to the present invention is described in the following with reference to the enclosed figures showing:

#FIG. 1 a central office line card comprising a POTS-splitter according to the state of the art;

#FIG. 2 a further central office line card comprising a POTS-splitter according to the state of the art;

#As can be seen from FIG. 3 the central office line card 1 includes the switchable POTS-splitter 2 according to the present invention. The POTS-splitter 2 of the central office line card 1 is connected via a ring line 3 and a tip line 4 to a remote transmission unit having a separate POTS splitter to which a telephone and a data terminal is connected. The POTS-splitter 2 includes a low pass filter 5 of low order so that an impedance can be synthesized by the programmable SLIC for any country in the world. The low pass filter 5 is a passive filter including a first coil 5a and a second coil 5b. In a preferred embodiment the inductivity of the coils 5a, 5b is around 5 mHenry. The first coil 5a is connected to the ring line 3 and the second coil 5b is connected to the tip line 4.

#The low pass filter 5 according to the preferred embodiment of the present invention as shown in FIG. 3 includes further at least one capacitor 5c and a corresponding capacitor switch 5d for switching the capacitor 5c to the ring line in parallel to a ring signal generator g. The coil 5a connected to the ring line 3 is connected via a signal line 6 to an electronic switch device 7.

#The electronic switch device 7 includes four electronic switches 7a, 7b, 7c, 7d. The first switch 7a is a signal feeding switch and connected via a current measuring resistor a to the ring signal generator 9 which is grounded to earth via a line 10. The second electronic switch 7c of the electronic switch device 7 is connected via a line 11 to ground. The electronic switches 7b, 7d are connected via lines 12, 13 to a subscriber line interface circuit (SLIC) 14 which is connected via lines 15, 16 to a CODEC-circuit 17. The codec 17 is a device for converting analog signals to digital signals and vice versa. The CODEC-circuit 17 is connected via a line 18 to a digital telephone network 19 such as an AFM or Frame relay based network so that the voice signals are transmitted over digital lines.