Line equipment device for telegraph lines

Claim 2

An electronic line equipment device for use in a telegraph line wherein said device connects subscribers'' line to selecting members of a semielectronic automatic switching installation is a central office wherein said device permits seizure of the line by a calling party and a called party and wherein said device blocks the line upon occurrence of faults, said device comprising a first transistor circuit branched off from the line and controlling the current along the line, a second transistor circuit branched off from the line and detecting the polarities of said line, a third transistor circuit connected to the second circuit and introducing a predetermined delay in the transmission of the polarity of the line to said selecting members of the installation in order to avoid false calls in response to transient signals, a fourth transistor circuit connected to the first circuit and indicating to said selecting members the free or busy state of the line equipment, and a fifth transistor circuit connected to the fourth circuit, said fifth circuit operating in the case of faults in the line.

Claim 3

The device according to claim 1, wherein the first circuit comprises first and second transistors, the second circuit comprises third and fourth transistors, the third circuit comprises a fifth transistor, the fourth circuit comprises a sixth transistor and the fifth circuit comprises a seventh and eighth transistor, the currents along the line being controlled by the first and second transistors, the first transistor of PNP type controlling a first wire of said line and the second transistor of NPN type controlling a second wire of said line, the third and fourth transistors, both of PNP type, detecting the polarities entering the first wire, the fifth transistor of PNP type introducing the predetermined delay into the transmission of the polarity of the first wire to the members of the installation, the sixth transistor of NPN type indicating to the selecting members the free or busy state of the line equipment, the seventh transistor of PNP type and the eighth transistor of NPN typE being used in the event of faults in the line, a neon lamp constantly indicating the state of the line equipment, the circuits being such that, in the rest state, only the first, second and third transistors are conducting, and when the calling party seizes the line the fourth and fifth transistors also become conducting and communicate the call to the members of the installation, the call being connected by the members of the installation, the first, second, third, fourth and fifth transistors become nonconducting and the neon lamp is lit up, and when the called party seizes the line the sixth transistor becomes conducting if the equipment is busy, but remains nonconducting if the equipment is free, and, when the call is connected, the first, second and third transistors become nonconducting, the neon lamp being lit up, so that, when a call is being effectively connected for conversation with both calling party and called party seizing the line device remains connected to the line only through very high impedances, while when a call is being blocked as a result of faults in the line the seventh and eighth transistors become conducting, the neon lamp flashes and the device cut off from the installation remains connected to the line either with the first three transistors or with the first five transistors in the conducting state until the faults causing the blocking have disappeared.

Claim 4

The device according to claim 2, wherein the first wire is connected to the collector of the first transistor and to the emitter of the third transistor, each connection taking place through a diode, the second wire being connected to the collector of the second transistor, the collector of the second transistor also being connected to the base of the third transistor, each of these connections taking place through a diode, the collector of the first transistor also being connected through a diode to the base of the second transistor, the rest state of the line being signified by a negative polarity on the first wire and by a ground potential on the second wire, the first transistor being conducting and thus rendering conducting the second transistor, and the first and second transistors being conducting and in turn rendering conducting the third transistor, the rest state of the device being characterized by the conducting state of the first, second and third transistors and by the nonconducting state of the other five transistors.

Claim 5

The device according to claim 3, wherein the emitter of the fourth transistor is connected to the collector of the third transistor and to ground through a resistor, the base of the fourth transistor being directly connected to ground, the collector of the fourth transistor being connected to the emitter of the fifth transistor through a diode and to the base of the fifth transistor through a capacitor and a diode, each of the electrodes of the capacitor also being connected to the negative polarity through a resistor, the collector of the fifth transistor being connected through a diode to a calling wire of members of said installation so that, when the line is brought into a calling state by a positive polarity on the first wire, the fourth transistor becoming conducting and producing a shift of the potentials at the electrodes of the capacitor, and the fifth transistor is temporarily rendered nonconducting as long as the discharge of the capacitor continues, the fifth transistor thereafter becoming conducting and transmitting the call to the members, the delay thus produced in the transmission permitting avoidance of false call notifications in response to transient signals.

Claim 6

The device according to claim 4, wherein when the call is connected by the members of said installation in the central office, a ground potential on a wire for holding the connection of the equipment, said ground potential emanating from a crossbar switch, and having the effect of blocking the current of the first transistor by short circuiting of a Zener diode in series with itS base, the first transistor becoming nonconducting and rendering nonconducting the second, third, fourth and fifth transistors, the nonconducting state of the first transistor also causing the neon lamp to light up, so that in the busy state, the connections to the line then being made only through nonconducting transistors or diodes, the device thereby being connected to the line with a very high impedance.

Claim 7

The device according to claim 5, wherein seizure of the line by the called party is detected by an availability test on the line equipment by means of a negative polarity applied to a free wire by the selecting members, said free wire being connected to the emitter of the sixth transistor, the emitter being connected to the base of the said transistor through a resistor and to a common point which is in turn connected to the wire for holding the connection line equipment and extending from the crossbar switch through a diode, and to an availability-confirming wire through a diode, the base of the sixth transistor also being connected to the wire for holding the line equipment connected, through a resistor and a diode, and the collector of the sixth transistor being connected to a busy wire which is in turn connected to a busy circuit, the result of the test being given by the availability-confirming and holding wires so that the busy state of the line equipment at the time of the test is translated by a ground potential on the holding wire coming from the crossbar switch, and the sixth transistor then becomes conducting and applies a negative polarity to the busy wire, thus signalling the said busy state, and the free state of the line equipment at the time of the test being given by a negative polarity on the availability-confirming wire, its consecutive busying when it is connected is also manifested by a ground potential on the holding wire, with the result that the sixth transistor is rendered conducting, the first, second and third transistors are rendered nonconducting and the neon lamp is lit up.

Claim 8

The device according to claim 6, further comprising a number of grouped lines each having a device wherein seizure of one of the lines by the called party is manifested by an availability test on the line equipment by means of a negative polarity applied to the free wire of a first line of said number, the busy wire of the first line being connected to the free wire of the second line, the busy wire of the second line being connected to the free wire of the nth line and the busy wire of the last of said number being connected to the busy circuit, the availability-confirming wire of each device of each wire of the grouped line being connected to selecting members, so that the call is sent from line to line until the first of the available lines is reached and it being possible for any number of grouped lines to be thus connected, the total resistance of the busy circuit being increased only by the internal resistance of a transistor in the conducting state for each busy line equipment, and an available equipment having been reached, its subsequent busying when it is connected is manifested by the fact that its sixth transistor becomes conducting, its first, second and third transistors becoming nonconducting and the neon lamp being lit up.

Claim 9

The device according to claim 7, wherein in the case of blocking when the line is seized by called party due to nonreturn of the positive polarity on the first wire after the normal transmission of a call by a positive polarity on the second wire, a ground potential appears on a fault wire of the crossbar switch connected to the base of the eighth transistor, said eighth transistor becoming conducting and rendering conducting the seventh transistor, which is then maintained conducting independently of the fault wire and said fault wire applying a ground potential through a diode, to the base of the sixth transistor and to the availability-confirming wire in order to give the busying of the line equipment in the case of A test, the collector of the eighth transistor being connected through a relaxation circuit to the neon lamp, which flashes as long as this blocking state lasts, the collector of the eighth transistor also being connected through a diode to a capacitor which becomes charged, the negative polarity still being on the first wire, the first, second and third transistors are conducting and this situation is maintained until a return of the positive polarity on the first wire producing the unblocking, the fourth and fifth transistors then becoming conducting and causing the discharge of the capacitor and a shift of the potentials at its electrodes, a positive voltage then rendering nonconducting the diode through which the base current of the seventh transistor was flowing, the latter being nonconducting and thus rendering nonconducting the eighth transistor, whose base no longer receives the ground potential, and when the call is connected by the members of the installation, the ground potential on the holding wire extending from the crossbar switch renders nonconducting the first five transistors and causes the neon lamp to be continuously lit up.

Claim 10

The device according to claim 8, wherein in the case of a permanent loop blocking, the first wire remaining at positive polarity although the call has been connected, a ground potential then appears on the fault wire of the crossbar switch connected to the base of the eighth transistor, the said transistor becoming conducting and rendering conducting the seventh transistor, which is then maintained conducting independently of the fault wire and the fault wire applying a ground potential through a diode to the base of the sixth transistor and to the availability-confirming wire in order to give the busying of the line equipment in the case of a test, the collector of the eighth transistor being connected through a relaxation circuit to the neon lamp, which flashes as long as this blocked state lasts, the first, second, third, fourth and fifth transistors being conducting, the positive polarity still being on the first wire and this situation being maintained until the return of the negative polarity of the first wire, which has the effect of rendering nonconducting the fourth and fifth transistors, the collector of the eighth transistor also being connected through a diode to a capacitor, which becomes charged, the arrival of a positive polarity at the first wire rendering conducting the fourth and fifth transistors which, in becoming conducting, cause the discharge of the capacitor and a shift of the potentials at its electrodes, a positive voltage then rendering nonconducting the diode through which the base current of the seventh transistor was flowing, the latter being rendered nonconducting and thus rendering nonconducting the eighth transistor, the base of which no longer receives the ground potential, and when the call is connected by the members of the installation, the ground potential on the holding wire coming from the crossbar switch renders nonconducting the first, second, third, fourth and fifth transistors and causes the neon lamp to the continuously lit up.

Claim 11

The device according to claim 9, wherein in the case of a blocking in a permanent loop in which the first wire remains at the positive polarity although the call has been connected, but interruption of this positive polarity or of the transient negative polarities of spurious origin can occur and result in the fourth and fifth transistors becoming nonconducting, the capacitors are nevertheless not sufficiently charged, the first for delaying the return of the fifth transistor into the conducting state when the fourth transistor becomes conducting again and the second for applying a sufficient positive voltage to the base circuit of the seventh transistor to render it nonconducting, whereby the previously existing blocked state is not thereby modified and the neon lamp continues to flash.