JPH0690300A - Facsimile modem - Google Patents

Abstract

PURPOSE:To detect a ringing tone (CNG) signal for reception during transmission of a called station discrimination (CED) signal and to reduce the burden of CNG signal detection processing in a CPU. CONSTITUTION:A sine wave generator 3 which generates a called station discrimination (CED) signal to be sent to a telephone line 11 at the time of incoming call in accordance with communication control procedures prescribed by the CCITT recommendation T.30, a notch filter 4 which stops the CED signal from a line interface 1, which outputs the CNG signal received from the telephone line 11 to which the CED signal is sent, and allows the CNG signal to pass through, and a sine wave detector 5 which detects the CNG signal from the output of the filter 4 are provided to constitute a facsimile MODEM.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facsimile modem, and more particularly to a facsimile modem having a communication procedure signal processing function.

[0002]

2. Description of the Related Art In a conventional facsimile modem, as shown in FIG. 2, a facsimile modem 22 and a sine wave binarization circuit 24 are connected via a line interface 21 to which a telephone line 11 is connected. The sine wave binarization circuit 24 outputs the detection pulse 15 to the host CPU 25. Control bus 1
The facsimile modem 22 controlled by the host CPU 25 by means of 4 has a sine wave generator 3 inside.

Next, the operation of the conventional example will be described. At the time of an incoming call in the communication procedure of the facsimile machine (Phase A)
At the called station side, the facsimile modem 22 receives a control command from the host CPU 5 via the control bus 14.
Drive the sine wave generator 3 in the facsimile modem 22,
A 2100 Hz called station identification (CED) signal is sent to the calling station as a procedure signal 12 through the line interface 1 to the telephone line 11.

On the other hand, in the phase A, a ringing tone (CNG) signal of 1100 Hz is transmitted from the calling station side. The CNG signal is indispensable for the automatic calling terminal, and 3 after call connection.
A 1100 Hz signal that continues for 0.5 seconds at an interval of 2 seconds is sent to the called station. The CNG signal is input to the sine wave binarization circuit 24 as the detection procedure signal 13 via the line interface 21, and the frequency component is displayed as the detection pulse 15 under the supervision of the host CPU 5.

[0005]

In this conventional facsimile modem, the CED from the called station in phase A is used.
Since the signal and the CNG signal from the calling station are emitted almost at the same time, the CNG signal from the calling station cannot be detected while the CED is being transmitted by the facsimile modem of the called station. External circuit that detects the CNG signal arriving outside the facsimile modem of
It was necessary to provide a sine wave detector for the CNG signal.

Further, the host CPU has to judge that it is a CNG signal by using the binarized CNG signal arriving at phase A as a detection pulse and the cout value of the number of detection pulses based on its own timer. Host C
There is a drawback that the load on the PU becomes excessive.

[0007]

The facsimile modem of the present invention is based on CCITT Recommendation T.264. An oscillator circuit for generating a called station identification signal to be sent to a telephone line when an incoming call is received in accordance with a communication control procedure defined by 30 and a reception ringing signal from the telephone line to which the called station identification signal is sent are output. It has a filter for blocking the called station identification signal from the line interface and passing the ringing tone signal, and a detector for detecting the ringing signal from the output of this filter.

[0008]

The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention.

This embodiment is based on CCITT Recommendation T.264. A sine wave generator 3 for generating a called station identification (CED) signal to be sent to a telephone line 11 when receiving a call according to a communication control procedure defined by 30 and a telephone line 11 for receiving a called station identification signal. A notch filter 4 that blocks the called station identification signal from the line interface 1 that outputs a ringing tone (CNG) signal and passes the ringing tone signal, and a sine wave detector 5 that detects the ringing signal from the output of the filter 4 are provided. Configured to have.

Next, the operation of this embodiment will be described. In the phase A of the communication procedure of the facsimile apparatus, the called facsimile modem 2 receives the sine wave generator 3 via the control bus 14 by the control command of the host CPU 6.
Is driven to generate 2100 Hz as a CED signal. The CED signal is sent as a procedure signal 12 to the telephone line 11 via the line interface 1. On the other hand, in the same phase A, the CNG signal from the calling station is transmitted through the line interface 1 at intervals of 3 seconds for 0.5 seconds in succession 110.
A 0 Hz signal is sent out as the detection procedure signal 13. The CED and CNG signals input at the same time are input to the CED signal 2 by the notch filter 4 in the facsimile modem 2.
The 100 Hz component is removed and output to the sine wave detector 5.
As a result, the 1100 Hz component of the CNG signal can be detected, and the detection result in the facsimile modem 2 is monitored by the host CPU 6 at an appropriate timing via the control bus 14 to transmit the CED signal in the full-duplex operation. Even in this case, the CNG signal can be detected.

[0011]

As described above, according to the present invention, an oscillating circuit for generating a called station identification signal to be sent to a telephone line when a call is received, and a reception call from the telephone line to which the called station identification signal is sent. The CED signal is provided by including a filter that blocks the called station identification signal from the line interface that outputs a tone signal and passes the ringing tone signal, and a detector that detects the ringing signal from the output from this filter. It is possible to detect the received CNG signal during transmission of the. Further, the load of the CNG signal detection processing is reduced in the CPU.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of an example of a conventional facsimile modem.

[Explanation of symbols]

 1 line interface 2 facsimile modem 3 sine wave generator 4 notch filter 5 sine wave detector 6 host CPU 11 telephone line 12 procedure signal 13 detection procedure signal 14 control bus

Claims (1)

[Claims] 1. CCITT Recommendation T. An oscillator circuit for generating a called station identification signal to be sent to a telephone line when an incoming call is received in accordance with a communication control procedure defined by 30 and a reception ringing signal from the telephone line to which the called station identification signal is sent are output. A facsimile modem comprising: a filter for blocking the called station identification signal from a line interface and passing the ringing tone signal; and a detector for detecting the ringing signal from the output of this filter.