Telephone isolation system

• US 4,143,250 A
• Filed: 12/13/1976
• Issued: 03/06/1979
• Est. Priority Date: 12/13/1976
• Status: Expired due to Term

• Current Assignee: TII Corporation
• Original Assignee: TII Corporation
• Inventors: Simokat, Frank L.
• Primary Examiner(s): Olms, Douglas W.
• Application Number:
  US05/749,610
• Time in Patent Office: 813 Days
• Field of Search: 179/175.3 R, 179/175.3 F, 179/2 A, 340/160
• US Class Current: 379/27.01
• CPC Class Codes: H04M 3/301 Circuit arrangements at the subscriber's side of the line

Abstract

The system disclosed transiently disconnects a subscriber'"'"'s telephone equipment and network from the service provider (e.g. telephone company) network for a predetermined period of time in response to a remote switching pulse to facilitate the execution of diagnostic measurements without the necessity of visiting the subscriber'"'"'s premises. The disconnect action is carried out by a two stage solid state circuit incorporating gate controlled devices such as SCRs together with RC networks whereby a capacitance is charged in response to the remotely originated switching pulse and then discharges to energize a switching relay and to maintain it energized for a predetermined period. In the energized state the switching relay isolates the subscriber network and its equipment from the telephone company network to permit the diagnostic measurements. The circuit design also provides improved noise suppression, as well as protection against spurious switching and certain overvoltage conditions. A modified version also provides means for detecting certain tip short conditions.

Claims

1. For use in a system between a communication provider and a subscriber of the type which includes a provider network and a respective subscriber network, and wherein said provider network includes means for transmitting diagnostic switching signals to said subscriber network, an isolation system for responding to said disagnostic switching signals to transiently disconnect said subscriber network from said provider network, said isolation system comprising:

(1) switching means connecting said provider network to said subscriber network in one state and disconnecting said networks in a second state;

(2) a first switch control circuit connected to said provider network and having (a) pulse responsive means connected to respond to a short duration diagnostic switching signal, and (b) energy storage means responsive to said pulse responsive means;

(3) a second switch control circuit including a controlled rectifier having a control circuit connected to be responsive to said energy storage means and an output circuit connected to control actuation of said switching means; and

(4) a charge circuit connected to said energy storage means for maintaining a charge on said energy storage means during periods when said networks are interconnected.

2. For use in a system between a communication provider and a subscriber of the type which includes a provider network and a respective subscriber network and wherein said provider network includes means for transmitting diagnostic switching signals to said subscriber network, a disconnect system for responding to said diagnostic switching signals to transiently disconnect said subscriber network from said provider network, said disconnect system comprising:

(1) switching means normally connecting said provider network to said subscriber network in one state and disconnecting said networks in a second state,

(2) switch control means including a capacitance discharge circuit connected to said switching means for controlling the state thereof, said capacitance discharge circuit having a time constant in excess of ten seconds, whereby said networks may be isolated from one another for substantial periods to facilitate diagnostic testing; and

(3) a capacitance connected in said capacitance discharge circuit and means for maintaining a charge on said capacitance during periods when said networks are interconnected.

3. For use in a system between a communication provider and a subscriber of the type which includes a provider network and a respective subscriber network and wherein said provider network includes means for transmitting diagnostic switching signals to said subscriber network, a disconnect system for responding to said diagnostic switching signals to transiently disconnect said subscriber network from said provider network, said disconnect system comprising:

(1) switching means normally connecting said provider network to said subscriber network in one state and disconnecting said networks in a second state, and

(2) switch control means including a capacitance discharge circuit connected to said switching means for controlling the state thereof, said switch control means includes a capacitance in said discharge circuit and further includes means connected to said provider network and said subscriber network for maintaining a charge of said capacitance during the periods when said networks are interconnected.