Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-12-31
2003-04-15
Rao, Seema S. (Department: 2666)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C379S350000
Reexamination Certificate
active
06549546
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a switch, and in particular to a call cut-off detection circuit for a switch and a method of the same which are capable of implementing a good quality call and enhancing a reliability of the switch by detecting a call cut-off based on a simple method.
2. Description of the Conventional Art
Generally, a call cut-off occurs during a call. The call cut-off case is classified into a case that a call is inputted from a telephone terminal and is allocated to an audio channel(PCM channel) at a base station and uses a trunk of a switch, and then is cut off, and a case that a call is cut off due to an external environment before a stop button of the telephone terminal is pushed. The above-described two cases are called a call cut-off.
FIG. 1
illustrates a conventional electric circuit which includes a processor
10
, a time switch unit
20
, a local link unit
30
, a central link unit
40
, and a space switch
50
.
The processor
10
controls a call process and a maintenance of a switch and controls the time switch
20
. The local link unit
30
outputs a 8-bit PCM data outputted from the time switch
20
to the central link unit
40
through a STM-1 framer, and the 8-bit PCM data inputted from the central link unit
40
is outputted to the time switch
20
. In addition, the space switch
50
switches the 8-bit PCM data inputted from the central link unit
40
by the highway, and outputs the 8-bit PCM data inputted from another subscriber or another switch to the central link unit
40
.
The time switch
20
includes a speech memory storing the 8-bit PCM data as a block for receiving the 8-bit PCM data from the subscriber and performing an interchange of the time slot, and a write address generator
12
and a read address generator
13
for generating a write and read address WA and RA to the speech memory
11
in accordance with a clock signal CP
2
of 16.384 MKHz and a frame pulse signal FP
2
of 8 KHz.
The operation of the conventional electric switch will be explained with reference to FIG.
1
.
The 8-bit PCM data inputted to an externally connected subscriber terminal is stored into the speech memory
11
by the channel in accordance with the write address WA outputted from the write address generator
12
, and the thusly stored 8-bit PCM data is outputted to the local link unit
30
in accordance with a read address RA outputted from the read address generator
13
. At this time, the read address generator
13
is controlled by the processor
10
. Therefore, the local link unit
30
outputs the 8-bit PCM data outputted from the speech memory
11
to the central link unit
40
and the space switch
50
through a high speed link of 155.520 Mbps.
When the 8-bit PCM data switched by the space switch
50
is inputted through the central link unit
40
and the local link unit
30
, the 8-bit PCM data is stored into the speech memory
11
by the channel in accordance with the write address WA outputted from the write address generator
12
. Therefore, the 8-bit PCM data stored in the speech memory
11
is outputted to the telephone terminal in accordance with the rear address RA outputted from the read address generator
13
.
However, in the conventional switch, if a call cut-off occurs, a switch operator is capable of detecting a call cut-off state only based on a report from a subscriber. Namely, there is not way to detect the call cut-off state in the conventional art. Therefore, the switch operator is not capable of quickly repairing the cut-off call, so that it is impossible to increase a reliability of the switch.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a call cut-off detection circuit for a switch and a method of the same which overcome the aforementioned problems encountered in the conventional art.
It is another object of the present invention to provide a call cut-off detection circuit for a switch and a method of the same which are capable of quickly detecting a call cut-off occurring during a call.
It is another object of the present invention to provide a call cut-off detection circuit for a switch and a method of the same which are capable of implementing a good quality call and enhancing a reliability of the switch by detecting a call cut-off based on a simple method.
To achieve the above objects, there is provided a call cut-off detection circuit for a switch which includes a time switch unit switching a first PCM data, a COB(Cut-Off Call Bit) processing circuit combining the first PCM data and a first call state data or separating the first PCM data and a second call state data from a second PCM data, a processor writing the first call state data into the COB processing circuit and judging the state of a call cut-off of a channel based on the second call state data separated by the COB processing circuit, and a local link unit connected between the COB processing circuit and a space switch for transmitting and receiving the second PCM data.
To achieve the above objects,.there is provided a call cut-off detection method for a switch which includes the steps of storing a first call state data into a COB processing circuit, combining a first PCM data inputted from the side of a telephone terminal and the first call state data and transmitting a second PCM data to the side of a space switch, checking whether the second PCM data is inputted from the side of the space switch, separating the second PCM data inputted from the side of the space switch into a first PCM data and a second call state data, and comparing the thusly separated second call state data and first call state data and judging whether a call cut-off of a corresponding channel occurred.
Additional advantages, objects and features of the invention will become more apparent from the description which follows.
REFERENCES:
patent: 4280217 (1981-07-01), Hafer et al.
patent: 5450485 (1995-09-01), Hamilton
patent: 5995494 (1999-11-01), Horikawa
Fleshner & Kim LLP
Harper Kevin C.
LF Information & Communications, Ltd.
Rao Seema S.
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