JPH05102965A - Incoming guard system in terminal adaptor - Google Patents

Abstract

PURPOSE:To prevent invalid charging to an incoming in the course of disconnection processing of a host by discriminating a state of an ER signal and an ER turn-off waiting flag, when an incoming call comes to a terminal adaptor, and receiving or refusing the incoming. CONSTITUTION:When an incoming call comes to a terminal adaptor 10, an incoming control part 12 discriminates a state of the present ER signal and an ER turn-off waiting flag 11 in an interface 13 at that time and determines whether the incoming call is received or refused. The flag 11 is set to turn-on, when a communication channel to the other part of a communication is established and set to turn-off by turn-off of the ER signal by an end of disconnection processing from a data terminal 14. Accordingly, when the terminal 14 is executing a disconnection processing, since the ER signal and the flag 11 are turned on, it is refused to receive the incoming. When its disconnection processing is finished, the flag 11 is turned off, and the control part 12 receives the incoming and returns an answer. In such a way, invalid charging to the incoming in the course of disconnection processing can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a terminal adapter (T) which is connected to an ISDN network and supports a circuit switching service.
It relates to the incoming call guard system in A).

TA supporting circuit switching service
The call is sent and received by the interface signal from the 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 performing the disconnection process of the previous communication, the TA may accept the new call, and improvement thereof is desired.

[0003]

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

FIG. 5 shows an example in which a data terminal (or a host) is connected via a terminal adapter in order to execute a circuit switching service by the ISDN network. In FIG. 5, reference numeral 50 denotes a host such as a computer (or data terminal equipment DTE: Data Terminal Equipment), and 51 denotes an RS23.
2C interface, 52 is a terminal adapter (indicated by TA) provided between the host 50 and the ISDN network, 53 is the ISDN network, and 54 and 55 are terminals A and B.
(Terminals A and B are terminals equipped with an ISDN-compatible control device).

The TA 52 controls transmission / reception with the ISDN network through the D channel and transmits / receives data with the B channel.
This is executed via the channel, and control of transmission / reception and transfer of transmitted / received data is performed via the interface 51 with the host 50. In this example, RS232C, which is widely used as an interface, is used.

Although a large number of signal lines can be used in the RS232C, only the necessary signal lines among them can be used. In the example of FIG. 6, the signal lines sent from the host 50 side to the TA 52 are SD (transmission data), E
R (Equipment Ready: represents the power on / off state of the host) and the like are provided, and signal lines sent from the TA 52 to the host 50 are RD (received data) and DR (Data s).
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. 5, the host 5
The sequence of 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 is in the state of generating the ER ON to notify that the communication with the TA 52 is possible, the terminal A
From the ISDN network to the TA 52 (reception of the SETUP message via the D channel), the T
A52 identifies that the ER signal is on and
Returns a response to the N network (transmits a CONNECT message).

After that, the TA 52 and the other terminal A and TA 5
Establishing synchronization between two (according to CCITT recommendation V110)
I do. When the synchronization can be established between the partner terminal A and the TA 52, the TA 52 informs the host 50 by turning on the DR signal that the host 50 can communicate, and the host 50 and the terminal A can communicate with each other. The communication state is established, and data is transmitted and received between the two.

When the communication is completed, the terminal A disconnects (DI
(SC message) is transmitted and TA is sent through the ISDN network.
Arriving at 52. On the other hand, the TA 52 sends a release (REL message) to the ISDN network and turns off the DR signal to notify the host 50 that the transmission with the terminal A is completed (disconnected). Upon receiving this 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, but usually a large number of lines (T on each line).
A52 is provided), it takes a certain amount of time to complete the cutting process. When this disconnection process ends, the host 50 turns off the ER signal.

[0011]

In FIG. 6 above,
The TA 52 allows the incoming call when the signal line ER from the connected host 50 is ON when the incoming call is received,
When disconnection is possible from both the host 50 and the terminal A after the end of communication, the disconnection process of the host 50 may be slower than the disconnection process of the TA 52, and a problem occurs if another incoming call is received at this time.

That is, the explanation will be made with reference to the example of FIG.
After the terminal 2 receives the disconnection message from the terminal A and turns off the DR signal to notify the host, the TA 52 immediately ends the disconnection process. After that, when an incoming call (SETUP message) sent from another terminal B is received, at this time, the ER signal from the host 50 is on, so a response (CON
NECT message) to the terminal B. However, when the host 50 completes the disconnection process with the terminal A, the ER signal is turned off. TA52 that received this signal
Disconnects because it ends communication with terminal B (DISC
Message) and is sent to the terminal B via the ISDN network.

In this case, the host 50 does not communicate with the terminal B, but on the ISDN network, a response is returned and an abnormal disconnection occurs after the communication is in progress, but charging is performed. there were.

It is an object of the present invention to provide an incoming call guard system in a terminal adapter capable of preventing invalid charges for incoming calls during disconnection processing by a host.

[0015]

FIG. 1 illustrates the principle of the present invention. In FIG. 1, 10 is a terminal adapter (TA), 11 is an ER off wait flag that holds the state of the ER signal, 12 is an incoming call control unit, 13 is an interface between TA and host, 14 is a data terminal (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 a previous call, and when the TA receives a call, only the state of the ER signal at that time is received. Instead, the state of the ER-off wait flag is identified, and when the termination processing for the previous call is completed, the incoming call is answered.

[0017]

When the TA10 receives an incoming call from the network, the incoming call control unit 1
In 2, the current ER signal in the interface 13 at that time and the state of the ER off wait flag 11 are discriminated to decide whether to accept or reject the incoming call. The ER-off wait flag 11 is set to ON when the incoming call control unit 12 accepts an incoming call and returns a response to the network (when a communication path is established), and is transmitted when the communication disconnection processing in the data terminal 14 is completed. It is set to off by turning off the incoming ER signal. Therefore, since the ER signal is on and the ER-off wait flag 11 is set to on while the data terminal 14 is executing the disconnection process due to the previous incoming call, when the next incoming call is made at that time Controls to reject the incoming call.

When the processing for disconnecting the previous incoming call is completed, the data terminal 14 turns off the ER signal.
Since the off-waiting flag 11 is set to off, when there is a subsequent incoming call, the incoming call control unit 12 controls the call 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 is a host such as a computer device, 21-1, 21-2 and 21-3 are TAs.
1 for the interface signal line that connects the
~ Ports 3, 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 by the D channel.
ssembly), 25 are LAPB and IS which are protocols on the host side for performing packet communication via the D channel.
A LAPB-LAPD exchange section for performing mutual conversion of LAPD which is a protocol on the DN network side, 26 is a circuit exchange data communication control section for performing data communication via another B channel, and 27 is connected to an analog telephone. The analog interface controller 28 is an S / T point interface to the ISDN network.

The circuit switching data communication control unit 23 (26 has the same configuration) includes a signal line state detection unit 230, an ER off wait flag 231, a D channel (Dch) message control unit 2.
32, V.I. A 110 synchronization establishment detector 233 is provided to guard incoming calls according to the present invention. That is, Dch
When there is an incoming call (reception of a SETUP message), the message control unit 232 detects the state 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 it.

The circuit switching data communication control units 23 and 2 shown in FIG.
The control operation in 6 will be described using the control flow of the terminal adapter shown in FIG. When the incoming call message is received (30 in FIG. 3), it is judged whether the ER off wait flag is off (at 31), and if it is on, rejection of the incoming call is performed (at 3).
2). In this case, the Dch message control unit 232 sends a rejection message.

When the ER off wait flag is off, it is judged whether or not the ER line is in the on state (at 33), and when it is off, the CI (Call Indicator) signal of the interface signal with the host side is turned on (at 34). ), And transmits a calling (ALERT) message to the network side (step 35). Next, the current E
It is judged whether the R signal is on (at 36), and when it is off, the process waits as it is, and when it is on, the CI signal of the interface signal is turned off (at 37).

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

FIG. 4 shows a sequence example of communication operation in the circuit switching connection according to the present invention. In the case of FIG. 4, the host,
The terminal adapter (TA), ISDN network, terminal A, and 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 is ready to accept the power supply, the ER is turned on (a in FIG. 4). After this, terminal A calls and ISD
When the TA is called through the N network (same as b), the response message is transmitted according to the flow of FIG. 3 (same as c). When the synchronization is established, the DR signal of the interface signal is turned on to the host (at the same d and e), and the ER off wait flag (231 in FIG. 2) is set to on.

After this, the communication state is set (f in FIG. 4),
When the disconnection is notified from the terminal A upon completion of the communication (at the same g), the TA turns off the DR signal in the interface signal to notify the disconnection (at the same h). This causes the host to start 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 (same j). In this case, the incoming call is immediately rejected, so no charges are applied.

After this, when the disconnection process in the host is completed, ER off is sent to TA (at the same k), and T
In A, the ER off wait flag (231 in FIG. 2) is set to off. Then, the ER signal ON indicating that the host can accept the signal again is generated (the same l).

Thereafter, when the terminal B again makes a call and receives the TA (m in FIG. 4), the ER off wait flag is off this time, and the current state of the ER signal is on. Send a reply message. After this, (d,
Similar to steps e and f), operations such as synchronization establishment, occurrence of DR ON, and communication in progress are executed.

[0030]

According to the present invention, it is possible to prevent invalid billing when a host receives a call during disconnection processing. In addition, for a terminal that makes a call to a host that intensively processes a large number of calls, it is likely that the host will encounter during disconnection processing during access, so disconnection occurs without the conventional communication. It is possible to prevent the occurrence of an abnormal state of doing.

[Brief description of 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 the circuit switching 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 is a sequence of communication operations in a conventional circuit switching connection.

[Explanation of symbols]

 10 Terminal Adapter (TA) 11 ER Off Wait Flag 12 Incoming Call Control Unit 13 Interface between TA and Host 14 Data Terminal (Host)

Claims (2)

[Claims] 1. A terminal adapter provided between a host and a switching network, which is connected to the host through an RS232C interface, is turned on when a communication path with a communication partner is established, and is terminated by disconnection processing in the host. An ER-off waiting flag that is set to an off state when the ER signal sent is detected to be off is provided, and when there is an incoming call, the incoming call control unit receives the incoming call based on the detection output of the ER-off waiting flag and the current ER signal. Incoming call guard method for terminal adapters, which controls whether to respond to or reject. 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 system for a terminal adapter, characterized in that the incoming call is answered when the current ER signal detection output is on, and the incoming call rejection is controlled at other times.