JP2633754B2 - Incoming call guard method in terminal adapter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal adapter (T) connected to an ISDN network and supporting a circuit switching service.
It relates to the incoming call guard method in A).

[0002] TA supporting circuit switching service
Is transmitting / receiving operation by an interface signal from a terminal (or host). With this interface signal, the TA that has received the disconnection notification from the communication partner activates the disconnection process for the terminal. However, if a new communication arrives at the TA while the terminal is executing the disconnection processing of the previous communication, the TA may accept the new call, and an improvement thereof is desired.

[0003]

2. Description of the Related Art FIG. 5 is an explanatory view of an interface between a conventional terminal adapter and a terminal, and FIG. 6 is a sequence of a communication operation in a conventional circuit switching connection.

FIG. 5 shows an example in which a data terminal (or host) is connected via a terminal adapter in order to execute a circuit switching service through an ISDN network. In FIG. 5, reference numeral 50 denotes a host such as a computer (or a data terminal DTE: Data Terminal Equipment);
2C interface, 52 is a terminal adapter (indicated by TA) provided between the host 50 and the ISDN network, 53 is an ISDN network, 54 and 55 are terminals A and B.
(Terminals A and B are terminals provided with an ISDN-compatible control device).

The TA 52 controls transmission and reception to and from the ISDN network through the D channel, and transmits and receives data to and from the ISDN network.
In addition to being executed via a channel, it performs outgoing / incoming control and transmission / reception data transfer control via an interface 51 with the host 50. In this example, RS232C which is generally widely used is used as an interface.

Although a large number of signal lines can be used in RS232C, only necessary signal lines among them can be used. In the example of FIG. 6, SD (transmission data), E
R (Equipment Ready: indicating the on / off state of the power supply of the host) and the like are provided, and RD (reception data), DR (Data s) are used as signal lines transmitted from the TA 52 to the host 50.
et Ready: indicates whether the adapter is ready to accept data) and CI (Call Indicator: incoming call display).

In the connection configuration shown in FIG.
A sequence of a communication operation when an interface such as 0 and TA52 is used will be described with reference to FIG. In FIG. 6, when the host 50 generates an ER-ON signal to notify that communication with the TA 52 is possible,
Receives an incoming call (reception of a SETUP message via the D channel) to the TA 52 via the ISDN network,
A52 identifies that the ER signal is on, and
Return a response to the N network (transmit a CONNECT message).

Thereafter, TA52 communicates with terminal A of the partner and TA5.
Synchronization between the two (according to CCITT recommendation V110)
I do. When synchronization is established between the partner terminal A and the TA 52, the TA 52 turns on the DR signal to notify the host 50 that communication is possible to the host 50, so that the host 50 and the terminal A can communicate with each other. The communication state is established, and data transmission and reception are performed between the two.

When the communication is completed, terminal A disconnects (DI
SC message) is transmitted to the TA via the ISDN network.
Arriving at 52. In response to this, the TA 52 transmits a release (REL message) to the ISDN network, turns off the DR signal, and notifies the host 50 that the transmission with the terminal A has been completed (disconnected). Upon receiving the DR signal off, the host starts disconnection processing.

When the host 50 detects this DR signal off, it terminates the application (software) related to the communication.
A52 is provided), and it takes a certain time to complete the disconnection process. When the disconnection process is completed, the host 50 turns off the ER signal.

[0011]

In FIG. 6 described above,
The TA 52 allows the incoming call if the signal line ER from the host 50 connected to the incoming call is on,
If the disconnection from both the host 50 and the terminal A is possible after the end of the communication, the disconnection processing of the host 50 may be slower than the disconnection processing of the TA 52, and a problem occurs if there is another incoming call at this time.

That is, referring to the example of FIG.
After receiving the disconnection message from the terminal A and turning off the DR signal to notify the host, the TA 52 immediately terminates the disconnection process. Thereafter, when an incoming call (SETUP message) transmitted from another terminal B is received, since the ER signal from the host 50 is on at this time, a response (CON
(NECT message) to the terminal B. However, when the host 50 completes the process of disconnecting from the terminal A, the ER signal is turned off. TA52 which received this signal
Terminates communication with terminal B (DISC
Message) and sends it to terminal B via the ISDN network.

In this case, although the host 50 does not perform communication with the terminal B, on the ISDN network, a response is returned and the communication is in a state of communication. there were.

It is an object of the present invention to provide an incoming call guard system in a terminal adapter which can prevent invalid charging in an incoming call during disconnection processing by a host.

[0015]

FIG. 1 is a diagram illustrating the principle of the present invention. In FIG. 1, reference numeral 10 denotes a terminal adapter (TA), 11 denotes an ER off wait flag for holding the state of an ER signal, 12 denotes an incoming call control unit, 13 denotes an interface between the TA and the host, and 14 denotes a data terminal (host) including the host. ).

According to the present invention, the terminal adapter is provided with an ER off wait flag indicating whether or not an ER off signal has been received from the data terminal for the previous call, so that when a call arrives at the TA, only the state of the ER signal at that time is displayed. Instead, it identifies the state of the ER off wait flag and responds to the incoming call when the termination processing for the previous call is completed.

[0017]

When a call is received from the network at TA10, the incoming call control unit 1
In step 2, the current ER signal in the interface 13 at that time and the state of the ER off wait flag 11 are determined to determine whether to accept or reject the incoming call. The ER-off wait flag 11 is set to ON when the incoming call is received by the incoming call control unit 12 and a response is returned to the network (when the communication path is established). The ER signal is turned off when the ER signal is turned off. Therefore, while the data terminal 14 is performing the disconnection processing due to the previous incoming call, the ER signal is on and the ER off wait flag 11 is set to on. Performs control to reject the incoming call.

When the previous incoming call disconnection processing is completed, the data terminal 14 turns off the ER signal.
Since the OFF wait flag 11 is set to OFF, when there is a subsequent incoming call, the incoming call control unit 12 performs control to accept the call and return a response.

[0019]

FIG. 2 is a block diagram of an embodiment, FIG. 3 is a control flow of a terminal adapter, and FIG. 4 is a sequence example of a communication operation in a circuit switching connection according to the present invention.

In FIG. 2, reference numeral 20 denotes a host such as a computer, etc., and reference numerals 21-1, 21-2, and 21-3 denote TAs.
Port 1 for the interface signal line that connects the
~ Ports 3 and 22 are terminal adapters (TA), 23
Is a circuit switching data communication control unit, and 24 is a PAD (Packet Assembly Dea) for performing packet transmission on the D channel.
ssembly) and 25 are LAPB and IS which are host side protocols for performing packet communication via the D channel.
A LAPB-LAPD exchange unit for mutually converting LAPD, which is a protocol on the DN network side, 26 is a circuit exchange data communication control unit for performing data communication via another B channel, and 27 is connected to an analog telephone. The analog interface control unit 28 is an S / T point interface for the ISDN.

The circuit-switched data communication control unit 23 (having the same configuration as that of the line-switching data communication unit) 26 includes a signal line state detection unit 230, an ER-off wait flag 231, and a D-channel (Dch) message control unit 2.
32, V.I. A 110 synchronization establishment detecting unit 233 is provided to guard incoming calls according to the present invention. That is, Dch
When there is an incoming call (reception of the SETUP message), the message control unit 232 detects the states of the signal line state detection unit 230 and the ER off wait flag 231 and determines whether to respond to the incoming call or reject the call.

The circuit-switched data communication control units 23 and 2 shown in FIG.
6 will be described with reference to the control flow of the terminal adapter shown in FIG. When an incoming call message is received (30 in FIG. 3), it is determined whether the ER off waiting flag is off (31), and if it is on, the incoming call is rejected (3).
2). In this case, a reject message is transmitted from the Dch message control unit 232.

When the ER off wait flag is off, it is determined whether or not the ER line is on (33). When the ER line is off, the CI (Call Indicator) signal of the interface signal with the host is turned on (34). ), A calling (ALERT) message is transmitted to the network side (id. 35). Next, the current E
It is determined whether the R signal is on (36), and if it is off, the process waits as it is. If it is on, the CI signal of the interface signal is turned off (37).

Thereafter, as in the case where the ER line is on in step 33, the host is in a receivable state, so that a response (CONNECT) message is transmitted (38), and 110 is established or not. 11
0 based on the output of the synchronization establishment detecting section 233 (3 in FIG.
9), when the connection is established, the connection between the host and the partner terminal is made by the B channel (40), and then the ER off wait flag (231 in FIG. 2) is set to on (41). Thereafter, communication between the host 20 and the partner terminal via the ISDN network is performed, and the signal line state detection unit 230 detects whether or not the ER line of the interface has been turned off during that time (see FIG. 4).
2) When it is detected that the switch is off, the ER-off wait flag is turned off (43), and the circuit-switched data communication control unit 23 becomes empty.

FIG. 4 shows a sequence example of a communication operation in a circuit-switched connection according to the present invention. In the case of FIG.
The terminal adapter (TA), the ISDN network, the terminal A and the terminal B are arranged in the same order as in FIG. 6, and the terminal adapter (TA) has the configuration shown in FIG. 2 and operates according to the control flow shown in FIG.

When the host can accept the data by turning on the power, the ER is turned on (FIG. 4A). After this, terminal A calls and ISD
When a call arrives at the TA through the N network (b), a response message is transmitted according to the flow of FIG. 3 (c). When the synchronization is established, the DR signal of the interface signal is turned on (d, e) for the host, and the ER off wait flag (231 in FIG. 2) is set on.

After that, the communication state is established (f in FIG. 4).
When the disconnection is notified from the terminal A due to the end of the communication (g), the TA turns off the DR signal in the interface signal to notify the disconnection (h). As a result, the host starts the disconnection process. During this disconnection process (until the ER-off is generated from the host), if a call originated by another terminal B arrives at the TA (Same i), the TA has the ER-off wait flag set to ON. Therefore, a disconnection (call rejection) message is transmitted to the partner terminal B via the ISDN network (j). In this case, no charge is made because the incoming call is immediately rejected.

Thereafter, when the disconnection processing in the host is completed, an ER-off is sent to the TA (the same k), whereby the T
At A, the ER off wait flag (231 in FIG. 2) is set to off. Subsequently, an ER signal ON indicating a receivable state is generated again from the host (1).

Thereafter, when the terminal B calls again and arrives at the TA (m in FIG. 4), the ER-off wait flag is now off, and the current state of the ER signal is on. Send the response message. After this, (d,
As in e and f), operations such as establishment of synchronization, occurrence of DR on, and communication state are executed.

[0030]

According to the present invention, it is possible to prevent invalid charging when a host receives a call during disconnection processing. Also, for a terminal that makes a call to a host that processes many calls in a concentrated manner, the disconnection occurs without performing the conventional communication because the host is likely to encounter the disconnection process at the time of access. This can prevent the occurrence of an abnormal state.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a configuration diagram of an embodiment.

FIG. 3 is a control flow of a terminal adapter.

FIG. 4 is a sequence example of a communication operation in a circuit-switched connection according to the present invention.

FIG. 5 is an explanatory diagram of an interface between a conventional terminal adapter and a terminal.

FIG. 6 shows a sequence of a communication operation in a conventional circuit-switched connection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Terminal adapter (TA) 11 ER OFF waiting flag 12 Incoming call control unit 13 Interface between TA and host 14 Data terminal (host)

Claims (2)

(57) [Claims] 1. A terminal adapter provided between a host and an exchange network and set to on when a communication path with a communication partner is established in a terminal adapter connected to the host by an RS232C interface. An ER off wait flag that is set to an off state upon detection of the sent ER signal off is provided. When there is an incoming call, the incoming call control unit determines the incoming call based on the ER off wait flag and the current ER signal detection output. An incoming call guard method in a terminal adapter, which controls whether the terminal responds or rejects the call. 2. The incoming call control unit according to claim 1, wherein the ER off wait flag is in an off state,
An incoming call guard method in a terminal adapter, wherein the incoming call is answered when the current ER signal detection output is on, and the incoming call is rejected at other times.