Holdup alarm system

Claim 2

Holdup alarm apparatus for use in an electrical protection system at a protected premises, said system having a local protection circuit and being coupled to a central station over a transmission line having a high side and a low side, the central station having a cuRrent sensitive line break indicator and a source of direct current potential coupled in series between the high and low sides of the transmission line, the holdup alarm apparatus comprising: a. a manually operable switch having break contacts interconnecting the high side of said transmission line and one end of said local protection circuit and having make contacts; b. means interconnecting the other side of said local protection circuit and the low side of said transmission line; c. an electronic switching device; d. means including said make contacts coupling said electronic switching device between the high and low sides of said transmission line when said manually operable switch is operated; and e. an astable multivibrator operatively coupled to said electronic switch alternately to open and close said electronic switch thereby alternately to intercouple and uncouple the high and low sides of said transmission line at a rate determined by the repetition rate of said multivibrator alternately to cause current to flow in said transmission line and to break said transmission line thereby to subject said break indicator at said central station alternately to periods of current flow and periods of reduced current flow as a signal indication of operation of said manually operable switch.

Claim 3

Holdup alarm apparatus for use in an electrical protection system at a protected premises, said system having a local protection circuit and being coupled to a central station over a transmission line having a high side and a low side, the central station having a current sensitive break indicator and a source of direct current potential coupled in series between the high and low sides of the transmission line, the holdup alarm apparatus comprising: a. a manually operable switch having break contacts interconnecting the high side of said transmission line and one end of said local protection circuit and having make contacts; b. means interconnecting the other side of said local protection circuit and the low side of said transmission line; c. an electronic switching device; d. means including said make contacts coupling said electronic switching device between the high and low sides of said transmission line when said manually operable switch is operated; e. an astable multivibrator operatively coupled to said electronic switch alternately to open and close said electronic switch thereby alternately to intercouple and uncouple the high and low sides of said transmission line at a rate determined by the repetition rate of said multivibrator; f. means including said break contacts, when closed, to render said multivibrator unoperated; and g. means including said make contacts, when closed, to render said multivibrator operative whereby said electronic switch is operated, alternately to cause current to flow in said transmission line and to break said transmission line thereby to subject said break indicator at said central station alternately to periods of current flow and periods of reduced current flow as a signal indication of operation of said manually operable switch.

Claim 4

Holdup alarm apparatus for use in an electrical protection system at a protected premises, said system having a local protection circuit and being coupled to a central station over a transmission line having a high side and a low side, the central station having a current sensitive break indicator and a source of direct current potential coupled in series between the high and low sides of the transmission line, the holdup alarm apparatus comprising: a. a manually operable switch having break contacts interconnecting the high side of said transmission line and one end of said local protection circuit and having make contacts; b. means interconnecting the other side of said local protection circuit and the low side of said transmission line; c. an electronic switching device; d. means including said make contacts coupling said electronic switching device between the high and low sides of said transmission line when said manually operable switch is operated; e. an astable multivibrator operatively coupled to said electronic switch alternately to open and close said electronic switch thereby alternately to intercouple and uncouple the high and low sides of said transmission line at a rate determined by the repetition rate of said multivibrator; f. means including said break contacts, when closed, to render said multivibrator unoperated; and g. means including said make contacts, when closed, to render said multivibrator operative whereby said electronic switch is operated, alternately to cause current to flow in said transmission line and to break said transmission line thereby to subject said break indicator at said central station alternately to periods of current flow and periods of reduced current flow as a signal indication of operation of said manually operable switch.

Claim 5

Holdup alarm apparatus as set forth in claim 2 in which said electronic switch comprises a transistor having a first electrode coupled to the high side of said transmission line, a second electrode coupled through said make contacts to the low side of said transmission line and a third electrode coupled to said multivibrator whereby a change in condition of said multivibrator changes the conductive condition of the circuit including said first and second electrodes.

Claim 6

Holdup alarm apparatus as set forth in claim 3 in which a Zener diode is intercoupled between said second electrode and said make contacts, said Zener diode being poled to break down when said transistor is conductive between said first and second electrodes.

Claim 7

Holdup alarm apparatus as set forth in claim 4 in which a capacitor is coupled in parallel with said Zener diode and to saiD multivibrator to provide operating potential for the latter when said transistor is not conductive.

Claim 8

Holdup alarm apparatus as set forth in claim 5 in which said multivibrator comprises second and third transistors operatively coupled between said second electrode of said first transistor and said make contacts, so as to become alternately conductive and nonconductive in sequence, one of said second and third transistors being arranged, when conductive, to bias said first transistor to conduction and, when not conductive, to bias said first transistor to nonconduction.

Claim 9

Holdup alarm apparatus as set forth in claim 2 in which said electronic switch comprises a first transistor and said multivibrator comprises second and third transistors, said transistors being operatively coupled to said transmission line to receive operating potential therefrom, said break contacts being arranged, when closed, to shunt said operating potential.

Claim 10

Holdup alarm apparatus as set forth in claim 7 comprising biasing means arranged to prevent operation of said multivibrator upon removal of said shunt, said biasing means being arranged to be shunted by said make contacts when the latter are closed.

Claim 11

Holdup alarm apparatus for use in an electrical protection system at a protected premises, said system having a local protection circuit and being coupled to a central station over a transmission line having a high side and a low side, the central station having a current sensitive break indicator, a tone responsive indicator and a source of direct current potential coupled in series between the high and low sides of the transmission line, the holdup alarm apparatus comprising: a. a manually operable switch having break contacts interconnecting the high side of said transmission line and one end of said local protection circuit and having make contacts; b. means interconnecting the other side of said local protection circuit and the low side of said transmission line; c. an electronic switching device; d. means including said make contacts coupling said electronic switching device between the high and low sides of said transmission line when said manually operable switch is operated; e. an astable multivibrator operatively coupled to said electronic switch alternately to open and close said electronic switch thereby alternately to intercouple and uncouple the high and low sides of said transmission line at a rate determined by the repetition rate of said multivibrator; f. means including said break contacts, when closed, to render said multivibrator unoperated; g. means including said make contacts, when closed, to render said multivibrator operative whereby said electronic switch is operated alternately to cause current to flow in said transmission line and to break said transmission line thereby to subject said break indicator at said central station alternately to periods of current flow and periods of reduced current flow as a signal indication of operation of said manually operable switch; and h. a tone generator at said protected premises and coupled in series with said transmission line to superimpose an alternating tone signal on the direct current flowing in said line, absence of said tone being detected by said tone responsive indicator as an indication of a fault in said transmission line.

Claim 12

Holdup alarm apparatus for use in an electrical protection system at a protected premises, said system having a local protection circuit and being coupled to a central station over a transmission line having a high side and a low side, the central station having a current sensitive break indicator, a tone responsive indicator and a source of direct current potential coupled in series between the high and low sides of the transmission line, the holdup alarm apparatus comprising: a. a manually operable switch having break contacts interconnecting the high side of said transmission line and one end of said local protection circuit and having make contacts; b. means interconnecting the other side of said local protection circuit and the low side of said transmission line; c. an electronic switching device; d. means including said make contacts coupling said electronic switching device between the high and low sides of said transmission line when said manually operable switch is operated; e. an astable multivibrator operatively coupled to said electronic switch alternately to open and close said electronic switch thereby alternately to intercouple and uncouple the high and low sides of said transmission line at a rate determined by the repetition rate of said multivibrator; f. means including said break contacts, when closed, to render said multivibrator unoperated; g. means including said make contacts, when closed, to render said multivibrator operative whereby said electronic switch is operated alternately to cause current to flow in said transmission line and to break said transmission line thereby to subject said break indicator at said central station alternately to periods of current flow and periods of reduced current flow as a signal indication of operation of said manually operable switch; and h. a tone generator at said protected premises and coupled in series with said transmission line to superimpose an alternating tone signal on the direct current flowing in said line, absence of said tone being detected by said tone responsive indicator as an indication of a fault in said transmission line.