Duplex interconnect/dispatch trunked radio system

• US 4,672,601 A
• Filed: 08/13/1986
• Issued: 06/09/1987
• Est. Priority Date: 12/06/1984
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ablay, Sewim F.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Scutch, III, Frank M.
• Application Number:
  US06/896,310
• Time in Patent Office: 300 Days
• Field of Search: 370/26, 370/97, 370/31, 370/76, 455/15, 455/16, 455/17, 455/54, 455/56, 179/170 R, 179/2 EB
• US Class Current: 370/277
• CPC Class Codes: H04W 4/10 Push-to-Talk [PTT] or Push-On-Call services
• CPC Class Codes: H04W 76/45 for Push-to-Talk [PTT] or Push-to-Talk over cellular [PoC] services
• CPC Class Codes: H04W 84/08 Trunked mobile radio systems

Abstract

A dispatch trunked radio system which provides duplex or simplex telephone interconnect communications to subscriber units is described. The system allows duplex capable trunked system subscriber units to establish a full duplex communication link with conventional land based telephone interconnect service in accordance with a method which unifies the operation of the trunked system subscriber units, a plurality of trunked system repeaters, a trunked system central control unit, and a telephone interconnect control unit. The method of the present invention also provides improved trunked system performance by allowing simultaneous transmission and reception of channel controlling information.

Claims

1. A system for dispatch trunking and simplex/duplex telephone interconnect communication, wherein both simplex and duplex subscriber units utilize a common central control unit, said system comprising:

(a) A system central control unit for generating signalling and control information in accordance with a predetermined signalling scheme;

(b) a plurality of duplex repeaters coupled to said central control unit for transmitting and receiving data and voice on assisgned frequencies;

(c) a plurality of duplex/simplex subscriber units having means for automatically generating both simplex and duplex signalling in accordance with a predetermined signalling scheme;

(d) a telephone interconnect control unit coupled to said system control unit for interfacing the trunking portion of the system to the telephone interconnect system, wherein said telephone interconnect control unit responds to instructions generated by said central control unit to establish either a simplex or duplex audio communication path.

2. The central control unit as in claim 1 further including:

(a) means for determining whether a duplex call has been requested;

(b) means for continuously monitoring the inbound voice channel for low speed connect tone;

(c) means for simultaneously transmitting a handshake signal from the system control unit to the simplex/duplex subscriber units on the outbound voice channel;

(d) means for disabling the outbound voice channel thereby terminating the call if simultaneous low-speed connect tone is not detected on the inbound voice channel.

3. The duplex capable mobile units of claim 1 wherein signalling received from said central control unit provides an indication of the signal transmission quality transmitted between said central control unit and said duplex/simplex subscriber unit.

4. A method for establishing a duplex call from a subscriber unit to a land based party, in a duplex interconnect/dispatch trunked radio system said method comprising the steps of:

(a) transmitting an inbound signalling word (ISW), to a central control unit, on a predetermined frequency, said ISW indicating that duplex interconnect call service is requested;

(b) receiving an outbound signalling word (OSW) from said central control unit, said OSW constituting a grant to the subscriber unit to operate on an assigned frequency;

(c) transmitting a connect tone for a predetermined period to said central control unit, on said frequency, while concurrently receiving a low-speed handshake signal transmitted from said central control unit;

(d) concurrently transmitting a sequential DTMF signal for a predetermined period, at the termination of said connect tone, while receiving a low-speed handshake signal, said DTMF signal comprising desired telephone interconnect dialing information;

(e) concurrently transmitting a voice and connect tone signal while receiving a voice signal combined with said low speed handshake signal, at the termination of said DTMF signal.

5. The method of claim 4 wherein the subscriber unit'"'"'s audio is muted when said lowspeed handshake signal of said method is interrupted.

7. The method of claim 4 wherein said central control unit transmits a disconnect signal to said subscriber unit before terminating a call.

6. A method for establishing a duplex call from a subscriber unit to a land based party, in a duplex interconnect/dispatch trunked radio system having a central control unit and a telephone interconnect control unit, said method comprising the steps of:

(a) receiving with said central control unit an inbound signalling word (ISW) from a subscriber unit, on a predetermined frequency, said ISW indicating that duplex interconnect call service has been requested by said subscriber unit;

(b) transmitting an outbound signalling word (OSW) to said subscriber unit, said OSW constituting a grant to the subscriber unit to operate on an assigned voice frequency;

(c) receiving a connect tone for a predetermined period from said subscriber unit, on said assigned frequency, while concurrently transmitting a dial tone to said subscriber unit; and

(d) establishing a connection with a telephone landline through the telephone interconnect control unit, and coupling said landline to said central control unit for communication with said subscriber unit.

8. A method for simplex or duplex telephone interconnect communication from a subscriber unit to the land based portion of a dispatch trunked radio system having a plurality of duplex-capable subscriber units, a plurality of duplex trunked repeaters operating on assigned frequencies, a telephone interconnect control unit and a central control unit, said method comprising the steps of:

(a) transmitting an inbound signalling word (ISW) from a duplex-capable subscriber unit, said ISW indicating whether dispatch or interconnect service has been requested;

(b) receiving said ISW and decoding it with the central control unit to determine whether simplex or duplex interconnect or dispatch service has been requested;

(c) initiating a simplex communication mode if a dispatch call type has been requested, by transmitting an outbound signalling word (OSW) to said subscriber unit, said OSW constituting dispatch channel granting information;

(d) initiating a duplex communication mode by coupling a telephone land-line to an assigned repeater through the telephone interconnect control unit and under the control of the central control unit, if telephone interconnect service was requested by a subscriber unit;

(e) transmitting an OSW from the central control unit to said subscriber unit, said OSW authorizing the subscriber to operate with the repeater assigned for telephone interconnect communication;

(f) concurrently transmitting dial tone and low-speed grant data from the central control unit to the subscriber unit on the voice channel until a sequential DTMF signal is received from the subscriber unit;

(g) concurrently transmitting low-speed grant data and receiving connect tone while sending received DTMF signals to the telephone network through the telephone interconnect control unit;

(h) concurrently transmitting and receiving voice signals accompanied by low-speed data grant from the central control unit to a subscriber unit and connect tone from the subscriber unit to the central control unit, respectively;

(i) terminating a call if an end-of-call signal is sent from the telephone interconnect control unit or a subscriber unit, or if no activity is detected on the communications channel for a predetermined period.

9. The method of claim 8 further including the steps of:

(j) continuously monitoring the subscriber units received data signal to determine whether a signal of good quality is being received;

(k) muting the subscriber units receiver audio channel if a signal of low quality is detected.

10. A system for dispatch trunking and simplex/duplex telephone interconnect communication, wherein both simplex and duplex subscriber units utilize a common central control unit, said system comprising:

(a) A system central control unit for generating signalling and control information in accordance with a predetermined signalling scheme;

(b) a plurality of duplex repeaters coupled to said central control unit for transmitting and receiving data and voice on assigned frequencies;

(c) a plurality of duplex/simplex subscriber units having means for automatically generating both simplex and duplex signalling in accordance with a predetermined signalling scheme; and

(d) a telephone interconnect control unit coupled to said system control unit for interfacing the trunking portion of the system to the telephone interconnect system, wherein said telephone interconnect control unit responds to instructions generated by said central control unit to establish a duplex audio communication path.

11. A method for establishing a duplex call from a subscriber unit to a land based party, in a duplex interconnect/dispatch trunked radio system, said method comprising the steps of:

(a) transmitting an inbound signalling word (ISW) to a central control unit, on a predetermined frequency, said ISW indicating that interconnect call service is requested;

(b) receiving an outbound signalling word (OSW) from said central control unit, said OSW constituting a grant to the subscriber unit to operate on an assigned frequency;

(c) transmitting a connect tone for a predetermined period to said central control unit, on said frequency, while concurrently receiving a low-speed handshake signal transmitted from said central control unit.

12. The method of claim 11 and further including the step of:

(d) concurrently transmitting a sequential DTMF signal for a predetermined period, at the termination of said connect tone, while receiving a low-speed handshake signal, said DTMF signal comprising desired telephone interconnect dialing information.

13. The method of claim 12 and including the further step of:

(e) concurrently transmitting a voice and connect tone signal while receiving a voice signal combined with said low speed handshake signal, at the termination of said DTMF signal.

14. The method of claim 11 wherein said subscriber unit will terminate audio signal processing when said low-speed handshake signal reception is interrupted.