Telephone exchange apparatus

Details Telephone exchange apparatus Telephone exchange apparatus

2001-02-15

2004-05-04

Ramakrishnaiah, Melur (Department: 2643)

Telephonic communications

Emergency or alarm communications

Central office responsive to emergency call or alarm

C379S037000, C379S050000, C379S093050

Reexamination Certificate

active

06731721

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to an exchange such as PBX (Private Branch Exchange) composed to allow to conveniently execute emergency call such as Enhanced 911 call.
2. Related Art
FIG. 17
shows a system for emergency call composed using PBX
10
. In this system, an E911 unit
4
to be connected to a CAMA (Centralized Automatic Message Accounting) line
7
, one of corresponding lines for realizing an Enhanced 911 call (called E911 call, hereinafter), is connected to the outside of the PBX
10
, to be used as adapter of the PBX
10
and the CAMA line
7
.
Here, an E911 call is an emergency call (911 call) of which function is enhanced. According to this E911 call, it is adopted an approach wherein caller ID information or the like are sent to a station upon originating of an emergency call and the station obtains the caller location information based on this information, apprising facilities for emergency, where fire-fighting or similar emergency team is watching, of this information. As a consequence, the emergency team can arrive at the origin of call without fail.
The E911 unit
4
is an interface for transmitting the caller ID or others via the CAMA line
7
and is provided with a procedure for sending the caller ID (MF tone signal) to the station via T1 (digital) or TIE (bus) line or the like.
To the PBX
10
of
FIG. 17
are connected an degital key telephone
2
and a standard telephone set
3
and, on the other hand, it is connected to the E911 unit
4
via a general purpose bus
6
such as TIE line, and is connected to the public network (PSTN)
5
via respective lines. The 911 unit
4
is connected to a 911 Tandem Office
8
via the CAMA line
7
.
Moreover, the PBX
10
comprises a control section
11
including a time switch
111
, a transmitting and receiving interface
12
, a digital line interface
13
, a DKT (digital key telephone) interface
14
, a standard telephone set interface
15
, and a station line interface
16
, the control section
11
and respective interfaces
12
to
16
being connected by a PCM highway (speech highway) L
1
and a data highway L
2
.
In addition, the E911 unit
4
is composed as shown in FIG.
18
. The E911 unit
4
includes a receipt detector
61
for detecting a call-in from the PBX
10
, a dial detector
62
for detecting dial data of DTMF signal originated from the PBX
10
, a CPU
63
for supervising and controlling operations of the E911 unit
4
and a CAMA line interface
64
to be connected to the CAMA LINE
7
. Plural elements other than the CPU
63
are provided with so as to allow simultaneously a plurality of E911 calls from the PBX
10
.
Upon arrival of a call-in signal from the PBX
10
, the call-in detector
61
detects it and inform the CPU
63
of receipt detection. Now, the CPU
64
waits that an extension number allocated to an extension telephone terminal sent by the PBX
10
be detected by the dial detector
62
. This extension number serves as an ANI (Automatic Numbering Identification) signal corresponding to the caller location information. Upon the detection of the transmitted extension number by the dial detector
62
, the CAMA line interface
64
closes the CAMA line
7
, sends a connect signal to 911 Tandem Office
8
and, moreover, transmits the extension number (ANI) detected. Owing to this, the 911 Tandem Office
8
obtains the caller location information based on this information and apprises facilities for emergency, where fire-fighting or similar emergency team is attending, of this information. At the same time, the PBX
10
will be connected to the CAMA line
7
via the call-in detector
61
and the CAMA line interface
64
, enabling the emergency call.
The emergency call operation by the PBX
10
mentioned above will be described in reference to the flow chart of FIG.
19
. Upon a dial input (S
501
) via the DKT interface
14
from the digital key telephone
2
, the control section
11
of the PBX
10
determines whether it is an E911 call or not (S
502
). In other words, if “911” is dial-input, it constitutes an E911 call, originating the step S
503
to capture a trunk leading to the E911 unit
4
through the digital line interface
13
(S
503
).
At that time, the control section
11
determines whether there is or not a vacancy in the CAMA line interface
64
inside the E911 unit
4
(S
504
), and if there exists the vacancy, calls in the E911 unit
4
and then change an ANI signal including ID information of the digital key telephone
2
into a DTMF signal and transmits the DTMF signal to the E911 unit
4
via the general purpose bus
6
for performing an E991 call (S
505
).
Here, the ANI corresponding to the caller location information is registered in the control section
11
of the PBX
10
in response to the extension telephone. The E911 unit
4
receives the ANI signal transmitted from the PBX
10
, converts it into MF tone signal and sends it to the 911 Tandem Office
8
through the CAMA line
7
. The 911 Tandem Office
8
has the composition for retrieving the database of caller location information ALI (Automatic Location Information) corresponding to the ANI signal and for delivering, from this information, an emergency message communication to a firehouse or the like nearest to the caller. Therefore, it can advantageously transmit surely and rapidly where an emergency message has been generated, without calling a PSAP (Public Safety Answering Point).
In the step S
502
of
FIG. 19
, if it is determined that it is not an E911 call, a call processing using the public network (PSTN)
5
shall be performed by the station interface
16
(S
506
). On the other hand, in the step S
504
, if there is no vacancy in the CAMA circuit interface
64
, an ordinary emergency call processing to call the nearest firehouse or the like using the public network
5
by the station line interface
16
shall be performed (S
507
).
As mentioned above, when an E911 call is to be made from the PBX
10
using the E911 unit
4
, if the CAMA circuit interface
64
in the E
9
11
unit
4
is occupied, the E911 call can not be made, even if there exists an interface (such as transmitting and receiving interface
12
) connected to an E911 call corresponding line by MF signal, because the PBX
10
is lacking for MF signal source though it includes a mechanism for transmitting a DTMF signal. To resolve this inconvenience, it has been necessary to dispose an MF signal source in the PBX
10
.
FIG. 20
shows a block diagram of the control section
11
provided with a MF signal source. In this example, an MF tone generation circuit
114
for generating more various MF tones than the dial key corresponding DTMF tone is added to the control section
11
in the PBX
10
, in addition to a DTMF tone generation circuit
113
for generating dial key corresponding DTMF tone, for increasing the kind of tones. Here, the tone output time range in respect to a PCM highway L
1
being limited by a main CPU
112
, the main CPU
112
will be loaded heavily.
For example, an MF tone output from the MF tone generation circuit
114
will be arranged to the channel
0
(CH
0
) to the channel
31
(CH
31
) as shown in (
21
A) of
FIG. 21
, to be transmitted as input stream for MF tone. There, the time switch
111
outputs to the channel
2
and thereafter in the PCM highway L
1
having channel
0
(CH
0
) to channel
31
(CH
31
), and this stream is shown by (
21
B) of FIG.
21
. Here, the digit output time interval of MF tone is defined to 60 mS±0.5 mS, so it becomes difficult to control the time interval when the main CPU
112
is loaded heavily.
Moreover, the PBX
10
will includes a MF signal source in addition to the MF signal source provided in the E911 unit
4
; as a consequence, it will be redundant to have double MF signal source in a system. On the other hand, as the E911 unit
4
is connected to the PBX
10
outside, when E911 call can not originated through the E911 unit
4
, it is necessary to verify whether the fault is due to the E911 unit
4
to network si

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