Off-hook telephone clearing system

• US 5,764,752 A
• Filed: 03/15/1996
• Issued: 06/09/1998
• Est. Priority Date: 03/15/1996
• Status: Expired due to Fees

• Current Assignee: South Tech Instruments, Inc.
• Original Assignee: South Tech Instruments, Inc.
• Inventors: Byrd, Jeffrey M., Waite, Tyler E.
• Primary Examiner(s): MATAR, AHMAD
• Application Number:
  US08/616,222
• Time in Patent Office: 816 Days
• Field of Search: 379/373, 379/375, 379/208, 379/32, 379/33, 379/80, 379/187, 379/387, 379/393, 379/377, 379/418
• US Class Current: 379/377
• CPC Class Codes: H04M 1/715 using two or more extensions per line cordless telephones H04M1/725
• CPC Class Codes: H04M 1/82 Line monitoring circuits for call progress or status discrimination for detecting caller identity H04M1/573
• CPC Class Codes: H04M 3/14 Signalling existence of persistent "off-hook" condition
• CPC Class Codes: H04M 9/02 involving a common line for all parties

Abstract

An off-hook telephone clearing system for a telephone line having at least two telephones connected thereto, comprising a howler tone detector connected to each telephone, and a telephone disconnect device having an input responsive to the howler tone detector for disconnecting a telephone being in off-hook condition from the telephone line. The clearing system may include a latching relay in the disconnect device. The latching relay may be mechanically coupled to the telephone hookswitch for delatching upon hang-up of the receiver.

Claims

1. An off-hook telephone clearing system for a telephone line having at least two telephones connected thereto comprising a howler tone detector connected to each telephone, a telephone disconnect device having an input responsive to the howler tone detector for disconnecting a telephone being in permanent off-hook condition from the telephone line;

wherein said disconnect device includes at least one break contact in series with a respective conductor of said telephone line; and

wherein the disconnect device further includes an input connected to said howler tone detector for activating said break contacts, said howler tone detector including a storage device for storing energy derived from the howler tone for energizing activation of said break contact.

2. An off-hook telephone clearing system according to claim 1, wherein said telephone clearing system includes line interfacing means having inputs connected to the line for electrically interfacing the clearing system to the line.

3. An off-hook telephone clearing system according to claim 2, wherein said clearing system includes a holding device for holding said disconnect device in disconnect condition for a given holding time after receipt of howler tone.

4. An off-hook telephone clearing device according to claim 1, wherein said disconnect device includes a relay having a relay coil in operative engagement with said break contacts.

5. An off-hook telephone clearing device according to claim 3, wherein said holding device includes at least one holding capacitor coupled to said disconnect device for holding said disconnect device in disconnect condition for said given holding time.

6. An off-hook telephone clearing device according to claim 5, wherein said howler tone detector includes at least one rectifier diode for rectifying said howler tone, said rectifier diode being coupled to said holding capacitor for charging said holding capacitor.

7. An off-hook telephone clearing device according to claim 1 including delay means connected between said disconnect device and said howler tone detector for delaying operation of said disconnect means for a given delay time.

8. An off-hook telephone clearing device according to claim 2, wherein said line interfacing means include at least one interfacing capacitor.

9. An off-hook telephone clearing device according to claim 2, wherein said line interfacing means include a transformer having a primary and secondary winding respectively connected to said telephone line and said howler tone detector.

10. An off-hook telephone clearing device according to claim 4 wherein said relay includes latching means for latching said relay in operated condition.

11. An off-hook telephone clearing device according to claim 10, wherein said latching means include a magnetically biased relay core for magnetically holding said relay in operated condition.

12. An off-hook telephone clearing device according to claim 10, wherein said latching means include at least one latching relay contact connected to said relay coil for holding said relay in operated condition.

13. An off-hook telephone clearing device according to claim 10, wherein said clearing device is combined with said telephone in a common housing.

14. An off-hook telephone clearing device according to claim 10, wherein said telephone has a hookswitch, including linkage means connecting said hookswitch with said latching means, wherein said linkage means are operative for resetting said latching means upon returning said telephone to on-hook state.