Subscriber line control apparatus to concurrently detect change in line state for subscriber lines and determine validity of timer device

• US 5,577,114 A
• Filed: 05/02/1995
• Issued: 11/19/1996
• Est. Priority Date: 07/09/1991
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Hatano, Takashi, Morita, Sumie, Takano, Ryouzi
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): WEAVER, SCOTT LOUIS
• Application Number:
  US08/434,122
• Time in Patent Office: 567 Days
• Field of Search: 379/190, 379/191, 379/192, 379/193, 379/270, 379/274, 379/277, 379/286, 379/287, 379/288, 379/297, 379/377, 379/381, 379/382, 379/383, 379/384-385
• US Class Current: 379/385
• CPC Class Codes: H04M 3/2272 Subscriber line supervision circuits, e.g. call detection circuits
• CPC Class Codes: H04Q 11/0407 using a stored programme control

Abstract

A subscriber line control device utilizes a scan input table and a last look table. The scan input table stores respective current line states of a plurality of analog subscriber lines. The last look table stores respective preceding line states of the plurality of analog subscriber lines and information for validating or invalidating a timer device. A valid timer device corresponds to when a monitoring process is required. The scan input table is compared with the last look table at every predetermined cycle. When they do not match, it is judged whether the line state has changed or if the timer device is validated. Based on the judging result, an analog subscriber line control is performed according to an instruction specified by a call processing unit. The analog subscriber control is any of a call origination monitor, a dial pulse monitor, and an on-hook and off-hook (HIT) monitor.

Claims

1. A subscriber line control device for accommodating a plurality of analog subscriber lines, comprising:

memory means;

a) for storing present on-hook and off-hook information indicating present line states for a plurality of subscriber lines, b) for storing previous on-hook and off-hook information indicating previous line states for said plurality of subscriber lines obtained in a previous scanning period, and c) for storing present timer information of a plurality of bits each respectively corresponding to the present on-hook and off-hook information for each of said plurality of subscriber lines and previous timer information of a plurality of bits each respectively corresponding to the previous on-hook and off-hook information for each of said plurality of subscriber lines, each of said plurality of bits of said present and previous timer information indicating a validity of a timer device for monitoring one of a) on-hook time for a monitoring process at each of said plurality of subscriber lines, b) off-hook time for a monitoring process of each of said plurality of subscriber lines and c) on and off time of dial pulses for a monitoring process of each of said plurality of subscriber lines, said validity of the timer device indicating a state wherein the timer device counts time when one of said monitoring processes is required;

detecting means for simultaneously detecting a change in each of the present and previous line states of each of said plurality of subscriber lines and for determining a validity of said timer device by comparing the previous on-hook and off-hook information with the present on-hook and off-hook information at predetermined intervals and comparing the previous and present timer information included in the previous and present on-hook and off-hook information, respectively; and

control means for a) validating said timer device using the present and previous timer information in said memory means corresponding to each of the plurality of subscriber lines if an instruction is issued via a subscriber line to require monitoring any of off-hook states, on-hook states, and dial pulses, and for b) counting one of the on-hook and off-hook time and the on and off time of dial pulses of the subscriber line through which the instruction is sent using said validated timer device if said detecting means detects a change in one of the states of the subscriber line through which the instruction is sent.

2. The subscriber line control device according to claim 1, wherein

said memory means comprises a first table in a first memory area for storing the present on-hook and off-hook information indicating each of the present line states of each of said plurality of subscriber lines and a second table in a second memory area for storing the previous on-hook and off-hook information indicating each of the previous line states of each of said plurality of subscriber lines, and said present and previous timer information being stored in said first and second table for a present and previous scanning period, respectively, and

said detecting means simultaneously detects a change in each of the present and previous line states of each of said plurality of subscriber lines and determines a validity of said timer device by determining a coincidence between the on-hook and off-hook information stored in said first table and the on-hook and off-hook information stored in said second table.

3. The subscriber line control device according to claim 2, wherein

said first table stores said present on-hook and off-hook information in a plurality of bits indicating the present line states of said plurality of subscriber lines, respectively;

said second table stores said previous on-hook and off-hook information in a plurality of bits indicating the previous line states of said plurality of subscriber lines, respectively;

one of said first and second tables includes permanently stored information of plural bits corresponding to the present line states and the previous line states of each of said plurality of subscriber lines, for invalidating the timer device by setting a bit to zero for monitoring the on-hook and off-hook time of each said subscriber line and the on and off time of dial pulses;

the other one of said first and second tables stores timer information of a plurality of bits, corresponding to the present line states and the previous line states of each of said plurality of subscriber lines, for validating and invalidating the timer device for monitoring the on-hook and off-hook time of each said subscriber line and for monitoring the on and off time of dial pulses;

said detecting means simultaneously detects a change in the line states of each said subscriber line and determines a validity of said timer device, by determining a coincidence between the on-hook and off-hook information stored in said first table and the on-hook and off-hook information stored in said second table;

said control means rewrites the timer information on a subscriber line for use in monitoring off-hook conditions into information indicating that said timer device for monitoring off-hook conditions is valid, when an instruction to monitor an off-hook condition is issued via the subscriber line, and starts the timer device to count the off-hook time if said detecting means detects that the line states of the subscriber line has changed from an on-hook state to an off-hook state;

said control means rewrites the timer information for use in monitoring the on-hook conditions corresponding to a subscriber line into information indicating that said timer device for monitoring on-hook conditions is valid, when an instruction is issued via the subscriber line to monitor an on-hook condition, and starts the timer device to count the on-hook time if said detecting means detects that the line states of the specified subscriber line has turned an off-hook state to an on-hook state; and

said control means rewrites the timer information for use in monitoring dial pulses corresponding to a subscriber line into information indicating that said timer device for monitoring dial pulses is valid, when an instruction is issued via the subscriber line to monitor dial pulses, and starts the timer device to count on and off time of dial pulses.

4. The subscriber line control device according to claim 2, wherein

said detecting means uses a comparison string instruction to simultaneously a) detect a change in each of the present and previous line states of each of said plurality of subscriber lines and b) determine a validity of said timer device by sequentially comparing said information in said first table with said information in the second table.

5. The subscriber line control device according to claim 1, wherein

said control means comprises congestion control means for setting a maximum number of events for call processes related to the on-hook, off-hook and line states and for limiting a number of issued events to be smaller than the set maximum number based on a scan performed periodically by said detecting means on each of the present and previous line states of each of said plurality of subscriber lines, and based on said validated timer device, by executing selected call processes if the number of issued events reaches the maximum number of events.

6. The subscriber line control device according to claim 2, wherein

said control means comprises congestion control means for setting a maximum number of events for call processes related to the on-hook, off-hook and line states and a maximum number of subscriber lines for monitoring dial pulses and for managing a number of events and a number of subscriber lines to be equal to or smaller than the set maximum numbers, respectively, by executing selected call processes if the number of events and the number of subscriber lines for monitoring dial pulses reach the maximum number of events and the maximum number of subscriber lines, respectively.

7. A subscriber line control device for accommodating analog and digital subscriber lines, comprising:

memory means;

a) for storing present on-hook and off-hook information indicating present line states for a plurality of subscriber lines, b) for storing previous on-hook and off-hook information indicating previous line states for said plurality of subscriber lines obtained in a previous scanning period, and c) for storing present timer information of a plurality of bits each respectively corresponding to the present on-hook and off-hook information for each of said plurality of subscriber lines and previous timer information of a plurality of bits each respectively corresponding to the previous on-hook and off-hook information for each of said plurality of subscriber line lines, each of said plurality of bits of said present and previous timer information indicating a validity of a timer device for monitoring one of a) on-hook time for a monitoring process of each of said plurality of subscriber lines, b) off-hook time for a monitoring process of each of said plurality of subscriber lines and c) on and off time of dial pulses for a monitoring process of each of said plurality of subscriber lines, said validity of the timer device indicating a state wherein the timer device counts time when one of said monitoring processes is required;

detecting means for simultaneously detecting a change in each of the present and previous line states of each of said plurality of subscriber lines and for determining a validity of said timer device by comparing the present on-hook and off-hook information with the previous on-hook and off-hook information at predetermined intervals and comparing the previous and present timer information included in the previous and present on-hook and off-hook information, respectively;

control means for a) validating said timer device using the present and previous timer information in said memory means corresponding to each of the plurality of subscriber lines if an instruction is issued via a subscriber line to require monitoring any of off-hook states, on-hook states, and dial pulses, and for b) counting one of the on-hook and off-hook time and the on and off time of dial pulses of the subscriber line through which the instruction is sent using said validated timer device if said detecting means detects a change in one of the states of the subscriber line through which the instruction is sent; and

congestion control means for setting a maximum number of events for call processes and a maximum number of subscriber lines for monitoring dial pulses and for managing a number of events and a number of subscriber lines to be equal to or smaller than the set maximum numbers, respectively, by executing selected call processes if the number of events and the number of subscriber lines for monitoring dial pulses reach the maximum number of events and the maximum number of subscriber lines, respectively.

8. A switching system including a subscriber line control device and a call processing device for accommodating a plurality of analog subscriber lines, said subscriber line control device comprising:

memory means;

a) for storing present on-hook and off-hook information indicating present line states for a plurality of subscriber lines, b) for storing previous on-hook and off-hook information indicating previous line states for said plurality of subscriber lines obtained in a previous scanning period, and c) for storing present timer information of a plurality of bits each respectively corresponding to the present on-hook and off hook information for each of said plurality of subscriber lines and previous timer information of a plurality of bits each respectively corresponding to the previous on-hook and off-hook information for each of said plurality of subscriber lines, each of said plurality of bits of said present and previous timer information indicating a validity of a timer device for monitoring one of a) on-hook time for a monitoring process of each of said plurality of subscriber lines, b) off-hook time for a monitoring process of each of said plurality of subscriber lines and c) on and off time of dial pulses for a monitoring process of each of said plurality of subscriber lines, said validity of the timer device indicating a state wherein the timer device counts time when one of said monitoring processes is required;

detecting means for simultaneously detecting a change in each of the present and previous line states of each of said plurality of subscriber lines and for determining a validity of said timer device by comparing the present on-hook and off-hook information with the previous on-hook and off-hook information at predetermined intervals the previous and present timer information included in the previous and present on-hook and off-hook information, respectively;

control means for a) validating said timer device using the present and previous timer information from said memory means corresponding to each of the plurality of subscriber lines if an instruction is issued via a subscriber line to require monitoring any of off-hook states, on-hook states, and dial pulses, and for b) counting one of the on-hook and off-hook time and the on and off time of dial pulses of the subscriber line through which the instruction is sent using said validated timer device if said detecting means detects a change in one of the states of the subscriber line through which the instruction is sent; and

congestion control means for setting a maximum first number of events associated with call processes in the subscriber line control device, a maximum second number of events associated with call processes between the subscriber control device and the call processing device, and a maximum number of subscriber lines for monitoring dial pulses, and for managing a first number of events, a second number of events, and a number of subscriber lines requesting monitoring to be equal to or smaller than the set maximum numbers, respectively, by executing selected call processes if the first number of events, the second number of events and the number of subscriber lines for monitoring dial pulses reach the maximum first number of events, the maximum second number of events and the maximum number of subscriber lines, respectively.

9. The subscriber line control device in the switching system according to claim 8, wherein

said memory means comprises a first table in a first memory area for storing the present on-hook and off-hook information indicating each of the present line states of each of said plurality of subscriber lines and a second table in a second memory area for storing the previous on-hook and off-hook information indicating each of the previous line states of each of said plurality of subscriber lines, and said present and previous timer information being stored in said first and second table for a present and previous scanning period, respectively, and

said detecting means simultaneously detects a change in each of the present and previous line states of each said plurality of subscriber lines and determines a validity of said timer device by determining a coincidence between the on-hook and off-hook information stored in said first table and the on-hook and off-hook information stored in said second table.

10. The switching system according to claim 9, wherein

said first table stores said present on-hook and off-hook information in a plurality of bits indicating the present line states of said plurality of subscriber lines, respectively;

said second table stores said previous on-hook and off-hook information in a plurality of bits indicating the previous line states of said plurality of subscriber lines, respectively;

one of said first and second tables includes permanently stored information of plural bits corresponding to the present line states and the previous line states of each of said plurality of subscriber lines, for invalidating the timer device by setting a bit to zero for monitoring the on-hook and off-hook time of each subscriber line and the on and off time of dial pulses;

the other one of said first and second tables stores timer information of a plurality of bits, corresponding to the present line states and the previous line states of each of said subscriber lines, for validating and invalidating the timer device for monitoring the on-hook and off-hook time of each said subscriber line and for monitoring the on and off time of dial pulses;

said detecting means simultaneously detects a change in the line states of each said subscriber line and determines said valid timer device, by determining a coincidence between the on-hook and off-hook information stored in said first table and the on-hook and off-hook information stored in said second table;

said control means rewrites the timer information on a subscriber line for use in monitoring off-hook conditions into information indicating that said timer device for monitoring off-hook conditions is valid, when an instruction to monitor an off-hook condition is issued via the subscriber line, and starts the timer device to count the off-hook time if said detecting means detects that the line states of the subscriber line has changed from an on-hook state to an off-hook state;

said control means rewrites the timer information for use in monitoring the on-hook conditions corresponding to a subscriber line into information indicating that said timer device for monitoring on-hook conditions is valid, when an instruction is issued via the subscriber line to monitor on-hook conditions, and starts the timer device to count the on-hook time if said detecting means detects that the line states of the specified subscriber line has turned an off-hook state to an on-hook state; and

said control means rewrites the timer information for use in monitoring dial pulses corresponding to a subscriber line into information indicating that said timer device for monitoring dial pulses is valid, when an instruction is issued via the subscriber line to monitor dial pulses, and starts the timer device to count on and off time of dial pulses.

11. The switching system according to claim 8, wherein

said subscriber line control device accommodates said plurality of analog subscriber lines and a plurality of digital subscriber lines.