Protector device

In a telephone exchange having secondary semiconductor protection equipment, the provision of a primary protection module for insertion into location means within the exchange, said primary protection module comprising:

• a housing,
• a plurality of contacts associated with the housing for connection between a line pair and the exchange,
• a voltage sensor including a pair of series-connected solid state semiconductor devices connectable across the line pair via said contacts and operable on receipt of a source of over-voltage to provide a conductive path therefor,
• a first fusible current sensor connectable in series with the first line of the pair via the contacts and electrically located between the voltage sensor and the exchange and operable to become open circuit on receipt of a predetermined current,
• a second fusible current sensor connectable in series with the second line of the pair via the contacts and electrically located between the voltage sensor and the exchange and operable to become open circuit on receipt of a predetermined current,
• said first and second fusible current sensors each including impedance means in series with a fusible element thereof so as to be electrically located between the fusible element and the exchange, and
• heat sensitive means adjacent the voltage sensor operable to electrically bypass the voltage sensor on detection of heating resulting from continuous conduction thereof whereby both extraneous power sources and surges are dealt with by the primary protection module without damage to the secondary protection equipment.

A protector device for electrical connection between a pair of telephone line conductors and a pair of input terminals in telephone exchange equipment to protect the exchange equipment against extraneous electrical power sources and surges, said protector device comprising:

• a pair of input contacts for connection to said pair of telephone line conductors;
• a pair of output contacts for connection to the input terminals of the exchange equipment;
• a series-connected plurality of solid-state fold-back diodes electrically connected across said input contacts for passing extraneous current from sources and surges of excessive voltage;
• a pair of heat sensitive by-pass contacts disposed to short circuit said input contacts in response to heating caused by prolonged current flow through said fold-back diodes;
• each input contact being connected to a respectively corresponding output contact by a series-connected fusible link and impedance element connected in that order between the input and output contacts;
• and
• each said impedance element including a resistance element disposed to transfer heat to an associated fusible link to assist its fusing at relatively low but prolonged extraneous current flows therethrough.