公开(公告)号：JPH03166853A

公开(公告)日：1991-07-18

申请号：JP23465190

申请日：1990-09-06

Applicant: KOREA ELECTRONICS TELECOMM ,  KORIA TELECOMMUN OOSORITEII

Inventor： DO YUN KIMU

IPC: H04L1/00 ,  H04L29/08 ,  H04M11/00 ,  H04N7/12

Abstract: PURPOSE: To secure switching to an image communication mode and electrically transmit high-image quality image information for a short time by providing a modem which has a modulating and demodulating function with a plural number of communication speeds and a transmitting and receiving means for a dial-tone multifrequency signal. CONSTITUTION: A modem 2 is connected to a system bus 7 and has a modulating and demodulating function with communication speeds of 9600, 4800 and 2400bps and a transmitting and receiving means for a dial-tone multi-frequency(DTMF) signal. At a 1st stage image control information is sent electrically at 9600bps communication speed to send out a series of binary 0 signals. At a 2nd stage, a bit where an error occurs is calculated and at a 3rd stage, the DTMF signal is used, if an error rate reaches a specific ratio, to adjust a speed with a reception side and to perform electric transmission by reducing its communication speed down to 2400bps. When the error rates does not reach the specific ratio, the image information is transmitted and received as normal. Consequently, switching to image communication mode is made securely, and the image information of high image quality of >=64 gray levels can be transmitted for a short time.