Protector circuit

Claim 2

A protector circuit for protecting a communication equipment from a surge voltage applied to at least one signal line connected to said equipment by a turning-on of voltage limiting means and a thyristor means connected in series with each other between said signal line and ground, characterized in that: said voltage limiting means is a bidirectional voltage limiting element; said thyristor means is a two-terminal bidirectional thyristor; and the breakdown voltage V B of said bidirectional voltage limiting element is slightly higher than the battery feed voltage V Bf on said signal line, and the sum of said breakdown voltage V B and said break-over voltage VBO of said bidirectional thyristor is lower than the breakdown voltage V R of said equipment and higher than the non-operation voltage V A .

Claim 3

The protector circuit according to claim 1, characterized in that: a plurality of signal lines are connected to said equipment, said series connection of the bidirectional voltage limiting element and bidirectional thyristor is connected between each said signal line and ground, said individual bidirectional thyristors having respective gate terminals connected together and held open without being connected to any other part.

Claim 4

A protector circuit for protecting a communication equipment from a surge voltage applied to one of a plurality of signal lines connected to said equipment by a turning-on of a thyristor means connected between said signal line and ground, characterized in that: said thyristor means is a bidirectional thyristor; a first bidirectional voltage limiting element is connected in series with said bidirectional thyristor, a second bidirectional voltage limiting element is connected between the gate and anode terminals of said bidirectional thyristor, the gate terminals of said second bidirectional voltage limiting elements are connected together and held open without being connected to any other part, the breakdown voltage V Bl of said first bidirectional voltage limiting element is slightly higher than the battery feed voltage V Bf on said signal line, the sum of said breakdown voltage V B1 , the breakdown voltage V B2 of said second bidirectional voltage limiting element and the gate-cathode voltage V GK of said bidirectional thyristor is lower than the breakdown voltage V R of said equipment and higher than the non-operation voltage V A , and the break-over voltage V BO of said bidirectional thyristor is higher than the breakdown voltage V B2 .

Claim 5

A protector circuit for protecting a communication equipment from a surge voltage applied to one of a plurality of signal lines connected to said equipment by a turning-on of a thyristor means connected between said signal line and ground, characterized in that: said thyristor means is a bidirectional thyristor; a first bidirectional voltage limiting element is connected in series with said bidirectional thyristor, a second bidirectional voltage limiting element is connected between the gate and anode terminals of said bidirectional thyristor, the gate terminals of said second bidirectional voltage limiting elements are connected together and held open without being connected to any other part, the breakdown voltage V Bl of said first bidirectional voltage limiting element is slightly higher than the battery feed voltage V Bf on said signal line, the sum of said breakdown voltage V B1 , the breakdown voltage V B2 of said second bidirectional voltage limiting element and the gate-cathode voltage V GK of said bidirectional thyristor is lower than the breakdown voltage V R of said equipment and higher than the non-operation voltage V A , and the break-over voltage V BO of said bidirectional thyristor is higher than the breakdown voltage V B2 .

Claim 6

The protector circuit according to claim 3, characterized in that: said bidirectional thyristor is provided on the ground side with respect to said bidirectional voltage limiting element.

Claim 7

A protector circuit for protecting a communication equipment from a surge voltage applied to one of a plurality of signal lines connected to said equipment by a turning-on of a thyristor means connected between said signal line and ground, characterized in that: said thyristor means is a three-terminal bidirectional thyristor; a bidirectional voltage limiting element is connected between the gate and anode terminals of each of said bidirectional thyristors, the gate terminals of said bidirectional voltage limiting elements are connected together and held open without being connected to any other part, the holding current of each said bidirectional thyristors is higher than the battery feed current to said signal line, the break-over voltage V BO of said bidirectional thyristor is higher than the breakdown voltage V B of said bidirectional voltage limiting element, and the sum of said breakdown voltage V B and the gate-cathode voltage V GK of said bidirectional thyristor is lower than the breakdown voltage V R of said equipment and higher than said non-operation voltage V A .

Claim 8

A protector circuit for protecting a communication equipment from a surge voltage applied to one of a plurality of signal lines connected to said equipment by a turning-on of a thyristor means connected between said signal line and ground, characterized in that: said thyristor means is a three-terminal bidirectional thyristor; a bidirectional voltage limiting element is connected between the gate and anode terminals of each of said bidirectional thyristors, the gate terminals of said bidirectional voltage limiting elements are connected together and held open without being connected to any other part, the holding current of each said bidirectional thyristors is higher than the battery feed current to said signal line, the break-over voltage V BO of said bidirectional thyristor is higher than the breakdown voltage V B of said bidirectional voltage limiting element, and the sum of said breakdown voltage V B and the gate-cathode voltage V GK of said bidirectional thyristor is lower than the breakdown voltage V R of said equipment and higher than said non-operation voltage V A .

Claim 9

The protector circuit according to claim 5, characterized in that: the gate terminals of said bidirectional thyristors are grounded through a common resistor.

Claim 10

The protector circuit according to claim 1, characterized in that: each said bidirectional thyristor has a gate terminal, a commercial power line is connected to said equipment, a second three-terminal bidirectional thyristor is connected between said commercial power line and ground, and the gate terminal of said second three-terminal bidirectional thyristor and the gate terminal of said bidirectional thyristor are connected together without being connected to any other part.

Claim 11

The protector circuit according to claim 2, 3 or 5, characterized in that: a commercial power line is connected to said equipment, a second three-terminal bidirectional thyristor is connected between said commercial power line and ground, and the gate terminal of said second three-terminal bidirectional thyristor and the gate terminal of said bidirectional thyristor are connected together.