Concentrator system capable of completing emergency calls under congested traffic

• US 4,839,892 A
• Filed: 08/29/1988
• Issued: 06/13/1989
• Est. Priority Date: 08/27/1987
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Sasaki, Yasutaka
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Jung, Min
• Application Number:
  US07/237,204
• Time in Patent Office: 288 Days
• Field of Search: 370/95, 379/37, 379/45, 379/49, 379/92, 379/243, 379/245, 379/201, 379/208
• US Class Current: 370/348
• CPC Class Codes: H04W 4/90 Services for handling of emergency or hazardous situations, e.g. earthquake and tsunami warning systems [ETWS]
• CPC Class Codes: H04W 40/02 Communication route or path selection, e.g. power-based or shortest path routing
• CPC Class Codes: H04W 76/50 for emergency connections
• CPC Class Codes: H04W 84/14 WLL [Wireless Local Loop]; RLL [Radio Local Loop]

Abstract

In a radio concentrator system formed by a central station and remote stations, demand-assigned data channels are constantly monitored to detect when they are congested. When an emergency call is received from a subscriber terminal, a dial tone is sent to the terminal if the emergency call occurs simultaneously with the detection of a congestion. On hearing the dial tone, the subscriber dials an emergency destination address, which is received by a remote station and compared with a list of predetermined addresses and verified if it matches one of the predetermined addresses. The dialed information is sent from that station to the central station, where it is relayed to a switched network. An emergency channel is established to the network for routing the emergency call. This channel may be permanently provided and demand-assigned in response to an emergency channel assignment request, or first selected by a remote station requesting an emergency call and access is granted by the central station if no collision occurs between competing emergency calls. Alternatively, no emergency channel is provided in the system and one of the data channels is cleared when an emergency call is detected simultaneously with the occurrence of a congestion. The cleared channel is used as an emergency channel to complete the emergency call.

Claims

1. A concentrator system for connecting subscriber terminals to a switched telecommunication network through a plurality of demand-assigned two-way data channels, comprising:

means for detecting when said data channels are congested;

means for detecting an emergency call from one of said subscriber terminals occurring simultaneously with the detection of said congested channels;

means for sending a dial tone to said one subscriber terminal when said emergency call is detected simultaneously with the detection of the congested channels to allow an emergency destination address to be dialled from said terminal and receiving said dialled emergency destination address;

means for verifying said emergency call by comparing said received address with a list of predetermined addresses; and

means responsive to the verification of said emergency call for transmitting said received emergency destination address from said system to said network and establishing an emergency channel between said subscriber terminal and said network.

2. A concentrator system as claimed in claim 1, wherein said emergency call is indicated by a hook flash signal generated when said one subscriber terminal momentarily depresses a switchhook.

3. A concentrator system as claimed in claim 1, further comprising means for clearing one of said data channels when said emergency call is detected simultaneously with said channel all busy and establishing said emergency channel through said cleared data channel.

4. A concentrator system for connecting subscriber terminals to a switched telecommunication network, said system having a central station and a plurality of remote stations to which said subscriber terminals are connected, said central station and said remote stations being interconnected by a two-way transmission link having a plurality of data channels and an auxiliary two-way channel:

wherein said central station comprises;

a plurality of central subscriber line interface circuits associated in a one-to-one correspondence to said subscriber terminals and connected to said switched telecommunication network;

a central controller cooperating with said central subscriber line interface circuits for selecting one of said data channels in response to a channel assignment request either from said network and said remote stations and generating a data channel selection signal identifying the selected data channel, and detecting when all of said data channels are busy and generating an all-busy signal;

central multiplexer/demultiplexer means for coupling said central subscriber line interface circuits to said selected data channels in response to said data channel selection signal, coupling one of said central subscriber line interface circuits which is associated with a subscriber terminal requesting an emergency call to said auxiliary channel, coupling said data channel selection signal and said all-busy signal to said auxiliary channel, coupling said channel assignment request transmitted from said remote stations on said auxiliary channel to said central controller and detecting an emergency destination address transmitted from said remote stations on said auxiliary channel; and

a dialling circuit for signalling said detected emergency destination address to said network,

wherein each of said remote stations comprises;

a plurality of remote subscriber line interface circuits connected respectively to said subscriber terminals;

register means associated respectively with said subscriber terminals for transmitting a dial tone to said emergency call requesting subscriber terminal and receiving said emergency destination address therefrom;

a remote controller cooperating with said remote subscriber line interface circuits for generating said channel assignment request in response to an outgoing call request from said subscriber terminals and detecting a simultaneous occurrence of said all-busy signal from said central station and an emergency call from said emergency requesting subscriber terminal, causing said register means to send dial tone to the emergency call requesting subscriber terminal in response to the detection of said simultaneous occurrence, and verifying said emergency call by detecting a coincidence between said received destination address with a list of predetermined emergency destination addresses; and

remote multiplexer/demultiplexer means for coupling said remote subscriber line interface circuits to said selected data channels in response to said data channel selection signal, coupling one of said remote subscriber line interface circuits to said auxiliary channel which is associated with said emergency call requesting subscriber terminal, coupling said channel assignment request and said emergency destination address of the verified emergency call to said auxiliary channel, and coupling said data channel selection signal and said all-busy signal transmitted from said central station on said auxiliary channel to said remote controller.

5. A concentrator system for connecting subscriber terminals to a switched telecommunication network, said system having a central station and a plurality of remote stations to which said subscriber terminals are connected, said central station and said remote stations being interconnected by a two-way transmission link having a plurality of commonly shared two-way data channels, a two-way signalling channel and a plurality of two-way emergency channels:

wherein said central station comprises;

a plurality of central subscriber line interface circuits associated in a one-to-one correspondence to said subscriber terminals and connected to said switched telecommunication network;

a central controller cooperating with said central subscriber line interface circuits for selecting one of said data channels in response to a data channel assignment request either from said network and said remote stations and generating a data channel selection signal identifying the selected data channel, selecting one of said emergency channels in response to an emergency channel assignment request from said remote stations and generating an emergency channel selection signal identifying the selected emergency channel, and detecting when all of said data channels are busy and generating an all-busy signal;

central multiplexer/demultiplexer means for coupling said central subscriber line interface circuits to said selected data channel in response to said data channel selection signal, coupling one of said central subscriber line interface circuits which is associated with a subscriber terminal requesting an emergency call to said emergency channel, coupling said data channel selection signal, said emergency channel selection signal and said all-busy signal to said signalling channel, coupling said data channel assignment request transmitted from said remote stations on said signalling channel to said central controller and detecting an emergency destination address transmitted from said remote stations on said emergency channel; and

a dialling circuit for signalling said detected emergency destination address to said network,

wherein each of said remote stations comprises;

a plurality of remote subscriber line interface circuits connected respectively to said subscriber terminals;

register means associated respectively with said subscriber terminals for transmitting a dial tone to said emergency call requesting subscriber terminal and receiving said emergency destination address therefrom;

a remote controller cooperating with said remote subscriber line interface circuits for generating said data channel assignment request in response to an outgoing call request from said subscriber terminals and generating said emergency channel assignment request in response to an emergency call from said emergency call requesting subscriber terminal, detecting a simultaneous occurrence of said all-busy signal from said central station and said emergency call, causing said register means to send dial tone to the emergency call requesting subscriber terminal in response to the detection of said simultaneous occurrence, and verifying said emergency call by detecting a coincidence between said received destination address with a list of predetermined emergency destination addresses; and

remote multiplexer/demultiplexer means for coupling said remote subscriber line interface circuits to said selected data channels in response to said data channel selection signal, coupling one of said remote subscriber line interface circuits which is associated with said emergency call requesting subscriber terminal to said emergency channel in reponse to said emergency channel selection signal, coupling said channel assignment request to said signalling channel, coupling said emergency destination address of the verified emergency call to said emergency channel, and coupling said data channel selection signal and said all-busy signal transmitted from said central station on said signalling channel to said remote controller.

6. A concentrator system for connecting subscriber terminals to a switched telecommunication network, said system having a central station and a plurality of remote stations to which said subscriber terminals are connected, said central station and said remote stations being interconnected by a two-way transmission link having a plurality of commonly shared, demand-assigned two-way data channels, a two-way signalling channel and a two-way emergency channel:

wherein said central station comprises;

a plurality of central subscriber line interface circuits associated in a one-to-one correspondence to said subscriber terminals and connected to said switched telecommunication network;

a central controller cooperating with said central subscriber line interface circuits for selecting one of said data channels in response to a channel assignment request either from said network and said remote stations and generating a data channel selection signal identifying the selected data channel, detecting whether a collision occurs between emergency call requests from said remote stations and generating an access grant signal when no collision is detected, and detecting when all of said data channels are busy and generating an all-busy signal;

central multiplexer/demultiplexer means for coupling said central subscriber line interface circuits to said selected data channel in response to said data channel selection signal, coupling one of said central subscriber line interface circuits which is associated with a subscriber terminal requesting an emergency call to said emergency channel, coupling said data channel selection signal and said all-busy signal to said signalling channel, coupling said access grant signal to said emergency channel, coupling said channel assignment request transmitted from said remote stations on said signalling channel to said central controller and detecting an emergency destination address transmitted from said remote stations on said emergency channel; and

a dialling circuit for signalling said detected emergency destination address to said network,

wherein each of said remote stations comprises;

a plurality of remote subscriber line interface circuits connected respectively to said subscriber terminals;

register means associated respectively with said subscriber terminals for transmitting a dial tone to said emergency call requesting subscriber terminal and receiving said emergency destination address therefrom;

a remote controller cooperating with said remote subscriber line interface circuits for generating said channel assignment request in response to an outgoing call request from said subscriber terminals and detecting a simultaneous occurrence of said all-busy signal from said central station and an emergency call from said emergency requesting subscriber terminal, causing said register means to send dial tone to the emergency call requesting subscriber terminal in response to the detection of said simultaneous occurrence, and verifying said emergency call by detecting a coincidence between said received destination address with a list of predetermined emergency destination addresses; and

remote multiplexer/demultiplexer means for coupling said remote subscriber line interface circuits to said selected data channels in response to said data channel selection signal, coupling one of said remote subscriber line interface circuits which is associated with said emergency call requesting subscriber terminal to said emergency channel, coupling said channel assignment request to said signalling channel and said emergency destination address of the verified emergency call to said emergency channel, coupling said access grant signal transmitted from said central station on said emergency channel to said remote controller, and coupling said data channel selection signal and said all-busy signal transmitted from said central station on said signalling channel to said remote controller.

7. A concentrator system for connecting subscriber terminals to a switched telecommunication network, said system having a central station and a plurality of remote stations to which said subscriber terminals are connected, said central station and said remote stations being interconnected by a two-way transmission link having a plurality of commonly shared, demand-assigned two-way data terminals and a two-way signalling channel:

wherein said central station comprises;

a plurality of central subscriber line interface circuits associated in a one-to-one correspondence to said subscriber terminals and connected to said switched telecommunication network;

a central controller cooperating with said central subscriber line interface circuits for selecting one of said data channels in response to a data channel assignment request either from said network and said remote stations and generating a data channel selection signal identifying the selected data channel, detecting when all of said data channels are busy and generating an all-busy signal, and specifying one of said data channels in response to an emergency call request from said remote stations and generating a data channel disconnect signal identifying said specified data channel;

central multiplexer/demultiplexer means for coupling said central subscriber line interface circuits to said selected data channels in response to said data channel selection signal, clearing said specified data channel and coupling one of said central subscriber line interface circuits which is associated with a subscriber terminal requesting an emergency call to said cleared data channel in response to said data channel disconnect signal, coupling said data channel selection signal, a said data channel disconnect signal and said all-busy signal to said signalling channel, coupling said data channel assignment request transmitted from said remote stations on said signalling channel to said central controller and detecting an emergency destination address transmitted from said remote stations on signalling channel; and

a dialling circuit for signalling said detected emergency destination address to said network,

wherein each of said remote stations comprises;

a plurality of remote subscriber line interface circuits connected respectively to said subscriber terminals;

register means associated respectively with said subscriber terminals for transmitting a dial tone to said emergency call requesting subscriber terminal and receiving said emergency destination address therefrom;

a remote controller cooperating with said remote subscriber line interface circuits for generating said channel assignment request in response to an outgoing call request from said subscriber terminals and detecting a simultaneous occurrence of said all-busy signal from said central station and an emergency call from said emergency requesting subscriber terminal, causing said register means to send dial tone to the emergency call requesting subscriber terminal in response to the detection of said simultaneous occurrence, and verifying said emergency call by detecting a coincidence between said received destination address with a list of predetermined emergency destination addresses; and

remote multiplexer/demultiplexer means for coupling said remote subscriber line interface circuits to said selected data channels in response to said data channel selection signal, clearing said specified data channel and coupling one of said remote subscriber line interface circuits which is associated with said emergency call requesting subscriber terminal to said cleared data channel in response to said data channel disconnect signal, coupling said channel assignment request and said emergency destination address of the verified emergency call to said transmission link, and coupling said data channel selection signal, said data channel disconnect signal and said all-busy signal transmitted from said central station on said signalling channel to said remote controller.