Combination coin telephone and extension circuit

Claim 2

A circuit for connecting an extension telephone set across the line terminals of a coin telephone set comprising, in combination, means for ensuring access to a common telephone line by said coin telephone irrespective of whether said extension telephone is in use, and means for precluding monitoring of said coin telephone by said extension telephone whenever said coin telephone is in usE initiated prior to an attempted use by said extension telephone, each of said means utilizing, in common, an in-line relay in parallel combination with solid state switching means, the coil of said relay being in series with one side of said telephone line, said coil being shunted by a first varistor and said switching means being shunted by a second varistor, a conducting path between said switching means and the speech network of said extension telephone set, said path including relay contacts responsive to the operation of said relay, said switching means comprising first and second transistors having the emitter electrodes thereof connected to one terminal of said relay coil and the collectors thereof connected to the other terminal of said relay coil, the base electrodes thereof being connected by way of said last-named contacts to the speech network of said extension telephone.

Claim 3

A circuit for connecting an extension telephone set across the line terminals of a coin telephone set comprising, in combination, means for ensuring access to a common telephone line by said coin telephone irrespective of whether said extension telephone is in use, and means for precluding monitoring of said coin telephone by said extension telephone whenever said coin telephone is in use initiated prior to an attempted use by said extension telephone, each of said means utilizing, in common, an in-line relay in parallel combination with solid state switching means, the coil of said relay being in series with one side of said telephone line, said coil being shunted by a first varistor and said switching means being shunted by a second varistor, a conducting path between said switching means and the speech network of said extension telephone set, said path including relay contacts responsive to the operation of said relay, said switching means comprising first and second transistors having the emitter electrodes thereof connected to one terminal of said relay coil and the collectors thereof connected to the other terminal of said relay coil, the base electrodes thereof being connected by way of said last-named contacts to the speech network of said extension telephone, wherein said second varistor is connected between said emitter electrodes and the base electrodes of said transistors.

Claim 4

A circuit for connecting an extension telephone set across the line terminals of a coin telephone set comprising, in combination, means for ensuring access to a common telephone line by said coin telephone irrespective of whether said extension telephone is in use, and means for precluding monitoring of said coin telephone by said extension telephone whenever said coin telephone is in use initiated prior to an attempted use by said extension telephone, each of said means utilizing, in common, an in-line relay in parallel combination with solid state switching means, the coil of said relay being in series with one side of said telephone line, said coil being shunted by a first varistor and said switching means being shunted by a second varistor, a conducting path between said switching means and the speech network of said extension telephone set, said path including relay contacts responsive to the operation of said relay, said switching means comprising first and second transistors having the emitter electrodes thereof connected to one terminal of said relay coil and the collectors thereof connected to the other terminal of said relay coil, the base electrodes thereof being connected by way of said last-named contacts to the speech network of said extension telephone, wherein said second varistor is connected between said emitter electrodes and the base electrodes of said transistors.

Claim 5

A circuit for connecting an extension telephone across the line terminals of a coin telephone set comprising, in combination, a relay coil connected in series with the ring lead of said coin telephone, solid state switching means connected in shunt with said relay coil, a first varistor shunting said relay coil, a second varistor shunting said switching means, means connecting said switching means to the ring side of said extension telephone set, said last-named means including a break contact responsive to the operation of said relay.

Claim 6

A circuit for connecting an extension telephone across the line terminals of a coin telephone set comprising, in combination, a relay coil connected in series with the ring lead of said coin telephone, solid state switching means connected in shunt with said relay coil, a first varistor shunting said relay coil, a second varistor shunting said switching means, means connecting said switching means to the ring side of said extension telephone set, said last-named means including a break contact responsive to the operation of said relay.

Claim 7

Apparatus in accordance with claim 3 further including means manually operable at said extension telephone for providing a shunt resistive termination in place of the speech network of said extension telephone set, thereby to ensure against the lockup of the totalizer of said coin telephone and further ensuring disconnection of said extension set from the line without, however, establishing an a-c short across said line.

Claim 8

Apparatus in accordance with claim 4 wherein said switching means comprises first and second transistors each having the collector-emitter path thereof in shunt relation with said relay coil, said means connecting said switching means including a conducting path from a terminal common to the base electrodes of said transistors, through said break contact and through switch hook make contacts of said extension telephone.