Multi-channel access (MCA) radio telephone system

• US 4,568,800 A
• Filed: 03/28/1984
• Issued: 02/04/1986
• Est. Priority Date: 03/30/1983
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Orikasa, Hiromi
• Primary Examiner(s): Brady, W. J.
• Application Number:
  US06/594,672
• Time in Patent Office: 678 Days
• Field of Search: 179/2 E-2 EC
• US Class Current: 455/463
• CPC Class Codes: H04M 3/14 Signalling existence of persistent "off-hook" condition
• CPC Class Codes: H04Q 2213/13098 Mobile subscriber
• CPC Class Codes: H04Q 2213/13386 Line concentrator
• CPC Class Codes: H04Q 3/00 Selecting arrangements H04Q5/00 - H04Q11/00 take precedence
• CPC Class Codes: H04W 76/19 Connection re-establishment
• CPC Class Codes: H04W 76/25 Maintenance of established connections
• CPC Class Codes: H04W 76/30 Connection release
• CPC Class Codes: H04W 84/14 WLL [Wireless Local Loop]; RLL [Radio Local Loop]

Abstract

A multi-channel access (MCA) radio telephone system completes calls from conventional telephone systems over a plurality of shared radio channels to a base station serving a plurality of substations connected to a second telephone set. The MCA radio telephone system provides a method for clearing calls after they are completed. The method comprising the steps of: (a) detecting the hang-up at the first and conventional set involved in the clearing call; (b) maintaining the D.C. loop of the subscriber line to the first and conventional telephone set in response to the detection of an on-hook signal and returning the radio channel to an idle and waiting state; (c) detecting the hang-up of the second telephone set which is served by the base station re-establishing a radio channel between the base station and the substation involved in the call being cleared; (d) sending a release signal from the clearing substation through the re-established radio channel to the base station; and (e) opening the D.C. loop to the first and conventional telephone set in response to the release signal and placing the re-established radio channel into an idle and waiting state.

Claims

1. A method for releasing and clearing a call made between a first telephone set coupled to a base station and a second telephone set coupled to one of a plurality of substations, said call being via an established radio channel in accordance with the principle of a multi-channel access radio telephone system, said radio channel extending between said base station and one of said substations that is associated with said call, each of said substations having at least a second telephone set individually associated therewith, said multi-channel access radio telephone system including the steps of:

(a) detecting on-hook conditions responsive to the hanging-up of said first telephone set;

(b) maintaining a direct current loop across a subscriber line individually associated with said first telephone set in response to said detection of the on-hook condition and returning the established radio channel to an idle and waiting state;

(c) detecting on-hook conditions responsive to the hanging-up of a second telephone set and against establishing a radio channel, in accordance with the principle of said multi-channel access radio telephone system between said base station and the one of said substations that is associated with the on-hook second telephone set;

(d) sending a release signal from said substation through the re-established radio channel to said base station; and

(e) opening said direct current loop in response to said release signal and releasing said re-established radio channel into an idle and waiting state.

2. The method claimed in claim 1, and the added step of detecting the hanging-up of said first telephone set responsive to a busy tone sent from a side of said system to which said first telephone set is connected.

3. The method claimed in claim 1, wherein said Step (b) includes the steps of:

(b1) maintaining said direct current loop in response to the detection of the hanging-up of said first telephone set and sending a disconnect signal to said substation;

(b2) placing said base station into a waiting state after sending said disconnect signal; and

(b3) generating a local busy tone at said substation in response to said disconnect signal and turning off said substation.

4. The method claimed in claim 1, wherein said Step (e) includes the steps of:

(e1) maintaining said direct current loop in response to the detection of the hanging-up of said first telephone set and sending a line-lock disconnect signal to said substation;

(e2) placing said base station into a waiting state after sending said disconnect signal; and

(e3) turning off said line-lock substation in response to said line-lock disconnect signal.

5. The method claimed in claim 1, wherein said Step (c) includes the steps of:

(c1) detecting the hanging-up of said second telephone set and sending a call origination signal to said base station over a radio channel having an idle signal thereon;

(c2) removing said idle signal from said radio channel in response to said call origination signal;

(c3) sending an identification number signal of said substation from said substation over said radio channel to said base station in response to said removal of said idle tone;

(c4) returning said identification number signal from said base station over said radio channel to said substation; and

(c5) completing the re-establishment of a radio channel responsive to a reception of the identification number signal returned by said substation.

6. A multi-channel access radio telephone system having an exchange accomodating a plurality of telephone sets;

a base station coupled to said exchange by way of a plurality of first subscriber lines;

a plurality of substations connected to said base station via a plurality of shared radio channels, each of said substations having at least one telephone set associated therewith; and

a plurality of subscriber circuits coupled between said exchange and said base station, each of said subscriber circuits being individually associated with one of said first subscriber lines, each of said subscriber circuits having a busy tone detector for detecting a busy tone from the corresponding one of said first subscriber lines and a terminating circuit for forming a direct current loop by terminating said corresponding first subscriber line, said system comprising means responsive to a completion of a call between a first one of the plurality of telephone sets accommodated in said exchange and a second one among the telephone sets associated with said substations for operating said busy tone detector when said first telephone set is hung up first, means responsive to said operation of said busy tone detector for applying a termination to said direct current loop for maintaining a connection of said first subscriber line with said first telephone set involved in said completed call;

means for thereafter releasing a radio channel between said base station and said substation; and

means responsive to a hang-up at said second telephone set after release of said radio channel for re-establishing a radio channel between said base station and said substation;

means in said substation for sending a release signal over said re-established radio channel to the subscriber circuit associated with said first telephone set; and

means for opening said direct current loop by removing said terminating circuit in response to said release signal, and means for thereafter releasing said re-established radio channel.

7. A multi-channel access radio telephone system, as claimed in claim 6, wherein said radio channel is released responsive to a sending of a disconnect signal from said substation to said base station in response to the detection of the hanging-up of said first telephone set which terminates a transmission of said base station, and further terminates a transmission of said substation in response to said disconnect signal.

8. A multi-channel access radio telephone system, as claimed in claim 7, and means in said substation for supplying a local busy tone to said second telephone set in response to said disconnect signal.

9. A multi-channel access radio telephone system, as claimed in claim 6, wherein said subscriber circuit is in a concentrator coupled between said exchange and said base station, and said first subscriber lines comprising n pairs of subscriber lines extending between said exchange and said concentrator and m pairs of subscriber lines extending between said concentrator and said base station, said n and m being positive integers and n being greater than m.

10. A telephone system comprising a conventional central telephone exchange;

a plurality of subscriber stations coupled to said central exchange via subscriber lines;

a base station coupled to said central exchange;

a plurality of substations coupled to said base station via shared radio channels;

at least one telephone set coupled to each of said substations;

whereby calls are completed between said subscriber stations and said telephone sets via said subscriber lines, central exchange, base stations, radio channels, and substations;

means responsive to a completion of a call for dropping the radio channel involved in the completed call, whereby it immediately becomes available for use by other calls having shared access to the dropped radio channel;

means at said central exchange responsive to the completion of a call for sending a busy tone to and for terminating the line of a pertinent subscriber station previously involved in said completed call, whereby said line is held by the termination;

means at said base station for sending a disconnect signal to and for marking busy the pertinent substation previously involved in said completed call, whereby a line-locked state is established, means responsive to an on-hook signal at a pertinent telephone set previously involved in said completed call for re-establishing a radio channel between said pertinent substation and to said base station; and

means for releasing the held line and the re-established radio channel, thereby terminating said line-locked state.

11. The telephone system of claim 10 and a concentrator interposed between said central telephone exchange and said base station for controlling the sharing of said radio channels, busy tone detector means at said concentator, means responsive to the subscriber station going on-hook for transmitting busy tone, and means responsive to detection of said busy tone by said busy tone detector means for initiating said termination of said line-locked state.

12. The telephone system of claim 11 and two-to-four wire converter means in said concentrator for interfacing said central telephone exchange and said base station.

13. The telephone system of claim 11 and means for connecting a matched impedance resistance across the line of said pertinent subscriber station responsive to said busy tone detector detection of said busy tone, and means for disconnecting said resistance responsive to said re-established radio channel.

14. A telephone system comprising a plurality of land lines and a lesser plurality of radio channels which are shared by said land lines, concentration means for controlling the sharing of said radio channels by said land lines, means for completing calls between said radio channels and said land lines via said concentration means, means at said concentration means responsive to a completion of said calls for immediately dropping the radio channel involved in the completed call, whereby other land line immediately use the dropped radio channel, means at the opposite ends of said dropped radio channel responsive to a busy marking from equipment previously involved in said completed call for continuing marking busy and holding the equipment previously involved in said completed call, means responsive to an on-hook signal at equipment previously involved in said completed call for re-establishing a radio channel, and means responsive to signals transmitted over said re-established radio channel for dropping all equipment previously involved in said completed call, whereby said radio channels become available immediately after calls are completed and while the equipment involved in the completed call is still held busy until the substations previously associated with the completed call go on-hook.