Abandoned call control and indication

• US 5,475,745 A
• Filed: 09/04/1991
• Issued: 12/12/1995
• Est. Priority Date: 07/31/1991
• Status: Expired due to Term

• Current Assignee: Mitel Knowledge Corporation (Mitel Networks Corporation)
• Original Assignee: Zarlink Semiconductor Inc. (Microchip Technology Incorporated)
• Inventors: Boyle, Stephen J.
• Primary Examiner(s): Dwyer, James L.
• Assistant Examiner(s): Hong, Harry S.
• Application Number:
  US07/755,488
• Time in Patent Office: 1,560 Days
• Field of Search: 379/34, 379/45, 379/67, 379/88, 379/201, 379/217, 379/203, 379/204, 379/205, 379/249
• US Class Current: 379/45
• CPC Class Codes: H04M 11/04 with alarm systems, e.g. fire, police or burglar alarm systems
• CPC Class Codes: H04Q 3/625 Arrangements in the private branch exchange

Abstract

A method and apparatus for holding a line busy from which a party has disconnected and providing an indication to the other party that the first party has hung up. The invention operates by receiving a call in a telephone switching office from a first subscriber on an incoming line destined for a second subscriber, storing an indication signal signifying that the call has been received; in case the first subscriber has hung up, accessing the indication signal, and as a result sending a signal to the second subscriber which is indicative that the first subscriber has hung up. Such systems are useful in emergency call handling systems, such as 911 emergency call systems.

Claims

1. A method of handling telephone calls comprising:

(a) receiving a call in a telephone switching office from a first subscriber on an incoming line or trunk destined for a second subscriber, and completing the call to the second subscriber;

(b) storing in a memory an indication signal signifying that the call has been received via a particular incoming line or trunk;

(c) in case the first subscriber has hung up, accessing said memory and reading said indication signal, and as a result, sending a signal to the second subscriber which is indicative that the first subscriber has hung up;

(d) automatically holding the incoming line or trunk after the first subscriber has hung up, and releasing the incoming line or trunk upon sending said indicative signal to said second subscriber that the first subscriber has hung up.

2. A method as defined in claim 1, including the step of holding the incoming line or trunk in the case in which the first subscriber has hung up prior to the second subscriber answering said call, and sending the indication signal after the second subscriber has answered the call.

3. A method as defined in claim 1, in which said indicative signal is a tone.

4. A method as defined in claim 1, in which said indicative signal is a message.

5. A method as defined in claim 4, in which said message includes an identification of the incoming line.

6. A method of handling telephone calls comprising:

(a) receiving a call in a telephone switching office from a first subscriber on an incoming line or trunk destined for a second subscriber, and completing the call to the second subscriber;

(b) storing in a memory an indication signal signifying that the call has been received via a particular incoming line or trunk;

(c) in case the first subscriber has hung up after the second subscriber has answered the call, accessing said memory and reading said indication signal, and as a result, sending a signal to the second subscriber which is indicative that the first subscriber has hung up;

(d) automatically holding the incoming line or trunk in the case in which the first subscriber has hung up prior to the second subscriber answering the call, and releasing the incoming line or trunk upon sending said indicative signal to said second subscriber that the first subscriber has hung up, after the second subscriber has answered the call;

(e) holding the incoming line or trunk in the case in which the second subscriber has answered said call prior to the first subscriber hanging up, has placed the incoming line or trunk on hold, and has subsequently attempted to release the incoming line or trunk from hold after the first subscriber has hung up, and sending said indicative signal to the second subscriber indicative that the first subscriber has hung up after the incoming line or trunk has been attempted to be released from hold, and releasing said incoming line or trunk from hold only after the indicative signal has been sent.

7. A method of handling telephone calls comprising:

(a) processing a call in a telephone switching office from a first subscriber on an incoming line or trunk destined for a second subscriber on an outgoing line or trunk, and ringing the second subscriber via the outgoing line or trunk;

(b) storing an indication signal that the call has been received via a particular incoming line or trunk; and

(c) automatically holding the particular incoming line or trunk in case the first subscriber has hung up prior to the second subscriber answering the call, continuing to ring the second subscriber, and once the second subscriber has answered the ringing, sending a signal to the second subscriber indicative that the first subscriber has hung up, and then releasing the incoming line or trunk.

8. A method of handling telephone calls comprising:

(a) processing a call in a telephone switching office from a first subscriber on an incoming line or trunk destined for a second subscriber on an outgoing line or trunk, and completing the call to the second subscriber via the outgoing line or trunk;

(b) automatically holding the particular outgoing line or trunk in case the second subscriber has hung up, sending a signal to the first subscriber indicative that the second subscriber has hung up, and then releasing the outgoing line or trunk;

(c) automatically holding said particular outgoing line or trunk in the event the first subscriber has placed the outgoing line on hold and after the second subscriber has answered the call and the second subscriber has hung up while on hold, and then sending said indicative signal to said first subscriber after his attempt to release the outgoing line or trunk from hold, and releasing the outgoing line or trunk from hold upon said indicative signal having been sent.

9. A method as defined in claim 8, in which said indicative signal is a tone.

10. A method as defined in claim 8, in which said indicative signal is a message.

11. A method as defined in claim 10, in which said message includes an identification of the incoming line.

12. A telephone switching system comprising:

(a) at least one peripheral controller,

(b) line and trunk circuits controlled by said peripheral controller,

(c) a central control for controlling said system including controlling the peripheral controller and switching of signals between line circuits and between line and trunk circuits to enable calls to be made between lines and between lines and trunks,

(d) a first random access memory (RAM) connected to the central control for storage of first signals indicative of predetermined lines and trunks designated as abandoned call handling (ACH) lines and trunks, and for storing associated signals indicative of the active state of the ACH lines and trunks,

(e) a second random access memory (RAM) connected to each of said at least one peripheral controller for storage of second signals indicative of whether a line or trunk associated with a particular call is an ACH line or trunk,

(f) means in said each of said at least one peripheral controller for transmitting a signal to said central control advising it of the existence of a seized line or trunk relating to a call; and

for receiving in response from said central control a third signal indicative of the line or trunk being an ACH line or trunk, if it is such a line or trunk, and storing said second signal relating to said third signal in said second RAM;

for transmitting a signal to the central control indicative of a subscriber connected to said seized line or trunk hanging up; and

for holding said seized line or trunk until receiving a release command signal from the central control.