JPH0375111B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] When making a call from a data communication terminal device to a telephone line, it is constantly monitored to see whether or not a call signal has arrived on the telephone line, and if a call signal is received, the call is made at a predetermined period. A flag to be reset is set, and the state of this flag is determined to control the automatic calling operation.

[Industrial application field]

The present invention relates to a method for detecting a calling signal in a data communication terminal device connected to a telephone line and having an automatic calling function.

[Conventional technology]

When a terminal device that is connected to a telephone line and has an automatic call function for data communication makes an automatic call, if a call signal is sent from the telephone exchange at the same time as the call is being made, a so-called line collision will occur and the device will not function properly. In order to prevent this, the ringing signal of the line must be monitored.

FIG. 3 shows a schematic configuration of a conventional paging signal detection method for a terminal device, and FIG. 4 is a waveform diagram for explaining its operation.

In FIG. 3, a terminal device 21 is a telephone line 20
A call signal detection circuit 23 detects the presence or absence of a call signal from the register 24, and turns on or off the ring bit 24a of the register 24 depending on the presence or absence of the signal.

When the terminal device 21 enters the automatic transmission mode, the CPU 25 of the control circuit reads the ring bit 24a of the register 24 at fixed short time intervals (several hundred milliseconds) and monitors the time for (T ₁ +T ₂ +α). . Here, for times T ₁ , T ₂ , and α,
As shown in FIG. 4a, among the intermittent periods of the calling signal, the duration of the signal is T ₁ , the pause time is T ₂ , and α (not shown) is an arbitrary additional time.
Note that at Japanese telephone exchanges, T ₁ and T ₂ are 1 second and 2 seconds, respectively. Therefore, the terminal device 21
When the terminal enters the transmission mode, it monitors the time for a period of 3 seconds or more, and if the ring bit 24a of the register 24 does not become "1" during this period, as shown in FIG. 4b, the terminal captures the line. Make an automatic call.

[Problem that the invention seeks to solve]

In the conventional terminal device, the ring bit 24a of the register 24 is turned on/off depending on the presence or absence of a calling signal as shown in FIG.
is set, and the flag is reset during the pause time T2. Therefore, when the conventional terminal device goes into the transmission mode and goes to read the contents of the ring bit 24a, it may be in the silent period of the pause time T2 (when the flag is reset).
It is necessary to monitor at least (T2+α) time,
The above-mentioned loss time occurs before starting the transmission operation.

In the previous example, there is a loss time of about 3 seconds after the automatic call mode is entered and before the actual call operation begins. On the other hand, it takes about 15 seconds for a terminal device to start data communication after it starts making a call, and it takes about 18 seconds including loss time from when it goes into automatic call mode until it is ready for data communication. This method takes time, and in order to reduce this time, there is a problem in that there is a loss time required for detecting the call signal.

[Means for solving problems]

The present invention provides a data communication terminal device connected to a telephone line with an interrupt control circuit 36 that generates an interrupt when a call signal detection circuit 33 detects a call signal, and a timer 39 that generates an interrupt when the control circuit 35 detects a call signal. When the timer 39 detects that a predetermined time has elapsed, the flag is reset.

[Effect]

According to the above configuration, since the timer monitors the presence or absence of a call signal and displays this using a flag, when the automatic call mode is entered, the control circuit 35
This allows the state of the flag to be identified and the presence or absence of a call signal to be immediately detected, thereby shortening the time required to shift to automatic call mode.

〔Example〕

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining its operation.

In FIG. 1, 30 to 35 respectively correspond to 20 to 25 in the conventional device shown in FIG.
5, 36 represents an interrupt control circuit, and 37 represents a memory.

Regardless of whether the terminal device 31 is in call mode or standby mode, the ring signal detection circuit 33 always performs a detection operation at fixed time intervals (several hundred ms).

When the call signal detection circuit 33 detects a call signal, the RING bit of the register 34 becomes "1" (see FIG. 2b), and at the same time, a call signal detection output is supplied to the interrupt control circuit 36.

When the interrupt control circuit 36 receives this output,
An interrupt signal is generated to the CPU 35 (see FIG. 2c).

When the CPU 35 receives the interrupt signal, it moves to detecting the cause of the interrupt. In this operation, the contents of the register 34 are read, the ring bit is identified, and if it is "1", the ring flag in the flag area 38 of the memory 37 is set (see FIG. 2d) and the timer 39 is started. (initialize) (see Figure 2 e).

Thereafter, the timer 39 counts time at a predetermined clock cycle. The timer 39 continues counting, and when the counted value exceeds the time T ₁ +T ₂ +α, the CPU 35 detects this and resets the ring flag in the flag area 38.

Also, if the next paging signal appears within the time T ₁ +T ₂ +α, the interrupt signal causes the ring flag to be reset and the timer 39 to be restarted.

In this way, the terminal device 31 always maintains the arrival state of the paging signal using the flag in the memory 37.

When the terminal device 31 enters the automatic call mode and makes a call, the CPU 35 checks the ring flag in the flag area 38, and if it is reset (off), the telephone line 3 is immediately switched off.
0 is switched to the oscillation circuit 32 to start the oscillation operation, and if the ring flag is set (on), the oscillation operation is performed after waiting for the ring flag to be reset. In the present invention, when a call signal is detected, the ring flag in the flag area 38 of the memory 37 is set by the CPU 35, and is reset by the timer 39 after a predetermined time (T1+T2+α) has elapsed. In other words, the flag area of the present invention retains the information of the detection of the calling signal for a period of time (T1+T2+α) as shown in FIG. 2d. Also, if a calling signal is arriving (T1 + T2 + α)
Since the ring flag is reset by the interrupt signal within the time of , flag 1 is maintained in the set state, and it can be immediately determined whether the ring flag is operable or not by looking at the ring flag during the transmission operation.
It should be noted that the present invention also makes it possible to reliably prevent collisions during takeoff and landing, as in the prior art.

[Effects of the Invention] The paging signal detection method according to the present invention immediately detects the arrival of a paging signal without waiting time by determining the state of the ring flag at that time when the terminal device is placed in automatic call mode. and if the flag is reset (off),
Calling operations can be started immediately.

[Brief explanation of drawings]

Figure 1 is a diagram showing the configuration of an embodiment of the present invention, Figure 2 is a diagram showing the configuration of an embodiment of the present invention.
3 is a waveform diagram showing the operation of each part of FIG. 1, FIG. 3 is a diagram showing the configuration of a conventional example, and FIG. 4 is a waveform diagram showing the operation of FIG. 3. In FIG. 1, 32: transmission circuit, 33: call signal detection circuit, 34: register, 36: interrupt control circuit, 37: memory, 39: timer.

Claims (1)

[Claims] 1. In a call signal detection method for a data communication terminal device connected to a telephone line and having an automatic dialing function, an interrupt control circuit 36 generates an interrupt signal every time a call signal is detected, and a flag is set in response to the interrupt signal. and a control circuit 35 that starts a timer 39 that counts a predetermined time equal to or more than one cycle of the calling signal, and when the timer 39 measures the predetermined time, resets the flag, and also determines the state of the flag and controls the flag. A call signal detection method characterized by automatically starting a call operation depending on the state.