초록 ▼

A protection arrangement for a two-wire line, such as a telephone subscriber line, includes a transformer having two primary windings and a secondary winding. The primary windings are connected in series with the wires of the line with phases such that common mode (longitudinal) currents on the line

A protection arrangement for a two-wire line, such as a telephone subscriber line, includes a transformer having two primary windings and a secondary winding. The primary windings are connected in series with the wires of the line with phases such that common mode (longitudinal) currents on the line induce a current in the secondary winding, whereas loop currents do not. The induced current in the secondary winding is amplified and used to trigger a protection device, such as a triac or SCR and diode bridge arrangement, to short circuit the line for the duration of any excessive current thereon.

대표청구항 ▼

A protection arrangement comprising: a transformer having two similar primary windings and a secondary winding, said primary windings having corresponding ends with respect to which currents flowing in the same direction in the two primary windings induce current in the secondary winding and equal c

A protection arrangement comprising: a transformer having two similar primary windings and a secondary winding, said primary windings having corresponding ends with respect to which currents flowing in the same direction in the two primary windings induce current in the secondary winding and equal currents flowing in opposite directions in the two primary windings substantially do not induce current in the secondary winding; protection means connected between said corresponding ends to the two primary windings; and control means responsive to induced current in the secondary winding of the transformer for triggering the protection means to provide a short circuit in the presence of excessive currents flowing in the same direction in the two primary windings; the protection means being arranged automatically to terminate said short circuit in response to termination of said excessive currents.