JP3581117B2

JP3581117B2 - Facsimile apparatus and facsimile communication method

Info

Publication number: JP3581117B2
Application number: JP2001257559A
Authority: JP
Inventors: 勝佐藤; 繁昭中村; 昌浩橋詰; 克彰安井; 均浅香
Original assignee: Kyocera Mita Corp
Current assignee: Kyocera Document Solutions Inc
Priority date: 2001-08-28
Filing date: 2001-08-28
Publication date: 2004-10-27
Anticipated expiration: 2021-08-28
Also published as: JP2003069798A

Description

【０００１】
【発明の属する技術分野】
本発明は、受信信号の変調方式が切り替わるファクシミリ装置及びファクシミリ通信方法に関するもので、特に、誤り再送方式となるＥＣＭ（ＥｒｒｏｒＣｏｒｒｅｃｔｉｏｎＭｏｄｅ）機能を備えたファクシミリ装置及びこのファクシミリ装置のファクシミリ通信方法に関する。
【０００２】
【従来の技術】
従来より、ファクシミリ装置において、通信時に電話回線上でノイズなどの影響を受けて、受信側で正しく画像信号が受信されなかったとき、送信側に画像信号の再送要求を行い、正しく受信されなかった画像信号の再送が行われる、ＥＣＭ機能を備えている。このＥＣＭ機能を利用して通信が行われているとき、図３のように、１フレームの２５６バイトの画像フレームを２５６フレーム送信した後、フェーズＤに切り替わって、ＰＰＳ−ＥＯＰ（ＰｅｒｔｉａｌＰａｇｅＳｉｇｎａｌ − ＥｎｄＯｆＰｒｏｃｅｄｕｒｅ）が送信側のファクシミリ装置より送信される。
【０００３】
ＰＰＳ−ＥＯＰを受信した受信側のファクシミリ装置は、ＥＯＰより最終ページの送信信号の送信が終了したことを認識するとともに、ＰＰＳよりＥＣＭ通信であることを認識する。このとき、送信された２５６フレームの画像信号の中に、ノイズが重畳されて正しく受信されなかったフレームがあった場合、図３のように、正しく受信されなかったフレームを指定するためのＰＰＲ（ＰｅｒｔｉａｌＰａｇｅ
Ｒｅｑｕｅｓｔ）が送信側のファクシミリ装置に送信される。
【０００４】
このＰＰＲを受信した送信側のファクシミリ装置は、ＰＰＲより受信側のファクシミリ装置で正しく受信されなかったフレームを認識し、そのフレームの画像信号を再送した後、ＰＰＳ−ＥＯＰを送信する。受信側のファクシミリ装置は、再送されたフレームの画像信号を受信すると、正しく受信されなかったフレームがある場合は、再度ＰＰＲが送信され、受信側及び送信側のファクシミリ装置で上述の通信動作が繰り返される。
【０００５】
これに対して、受信側のファクシミリ装置において、画像信号が正しく受信された場合は、図３のように、正しく画像信号を受信したことを示すＭＣＦ（ＭｅｓｓａｇｅＣｏｎｆｉｒｍａｔｉｏｎ）が送信される。そして、送信側のファクシミリ装置がＭＣＦを受信して、正しく画像信号が受信されたことを認識すると、図３のように、ＤＣＮ（Ｄｉｓｃｏｎｎｅｃｔ）が送信されて回線を切断することを受信側のファクシミリ装置に知らせる。
【０００６】
このようにＥＣＭ機能を利用してファクシミリ通信が行われたとき、正しく受信されなかったフレームの画像信号が、正しく受信されるまで再送されるため、受信側のファクシミリ装置に確実に画像信号を送信することができる。
【０００７】
【発明が解決しようとする課題】
しかしながら、送信された画像信号に重畳されたノイズが一時的なもので、断続的にエラーが発生する場合は、ＥＣＭ機能で対応することができるが、インパルスノイズや瞬断によって連続的にエラーが発生して、ファクシミリ装置に設けられたモデムでの受信信号が発散してしまった場合、画像信号の最終フレームであるＲＣＰ（ＲｅｔｕｒｎｔｏＣｏｎｔｒｏｌＰａｒｔｉａｌ）フレームの検出ができず、ＰＰＳ−ＥＯＰが検出できないことがある。これは、画像信号は１４４００ｂｐｓの通信速度で送信されているのに対して、ＰＰＳ−ＥＯＰは３００ｂｐｓの通信速度で送信されているというように通信速度が異なるため、画像信号の受信後ＰＰＳ−ＥＯＰを受信するのに、モデムの受信モードを切り換える必要があるためである。
【０００８】
即ち、１４４００ｂｐｓの通信速度に応じた受信状態で画像信号を受信している際、正常な動作を行っているときには、ＲＣＰフレーム検出後に３００ｂｐｓの通信速度に応じた受信状態に切り換えるが、画像信号の受信時にエラーが連続的に発生した場合、ＲＣＰフレームの検出ができないために、受信状態を切り換えることができずに、ＰＰＳ−ＥＯＰの受信が確認できない。よって、受信側のファクシミリ装置からＰＰＲを送信することができず、再送の要求ができない。尚、ＰＰＳ−ＥＯＰやＰＰＲといった、フェーズＢ及びフェーズＤにおいて３００ｂｐｓの通信速度で送受信される信号をＦＳＫ（ＦｒｅｑｕｅｎｃｙＳｈｉｆｔＫｅｙｉｎｇ）信号と呼ぶ。
【０００９】
このような問題を鑑みて、本発明は、ＥＣＭ機能を利用して通信動作を行っている際に部分ページ信号（ＰＰＳ）を確実に受信することが可能なファクシミリ装置及びファクシミリ通信方法を提供することを目的とする。
【００１０】
【課題を解決するための手段】
上記目的を達成するために、本発明のファクシミリ装置は、他のファクシミリ装置と信号の送受信を行うモデムと、受信した画像信号をフレーム毎に正しく受信されたか否かの確認を行うエラーチェック部とを有するとともに、前記モデムで正しく受信されなかったフレームが前記エラーチェック部で確認されたとき、通信相手となるファクシミリ装置に対して正しく受信されなかったフレームの画像信号の再送を求めるためのＥＣＭ機能を備えたファクシミリ装置において、前記エラーチェック部において、所定時間、前記モデムで正しく画像信号が受信されなかったときに、正しく受信されなかったフレームが連続したものと見なすとともに、前記モデムで正しく受信されなかったフレームが連続したことが確認されると、前記モデムの通信動作を、第１通信速度で送受信される画像信号を受信する第１状態から、第２通信速度で送受信される画像信号を受信する第２状態に強制的に切り換えることを特徴とする。
【００１１】
このようなファクシミリ装置において、エラーチェック部で、正しく受信されずにエラーの発生したフレームが連続して検出されると、前記モデムの通信速度を、例えば１４４００ｂｐｓといった通信速度の速い画像信号を受信する第１状態から、例えば３００ｂｐｓといった通信速度の遅いＦＳＫ信号を受信する第２状態に切り換える。こうすることによって、モデムが画像信号を正常に受信できない発散状態になったとき、画像信号の最終フレームとなるＲＣＰフレームの検出が不可能であっても、ＦＳＫ信号を受信することが可能な状態とされるので、通信相手となるファクシミリ装置の通信状態がフェーズＤに遷移したことを認識することができる。
【００１２】
このようなファクシミリ装置において、前記エラーチェック部において、所定時間、前記モデムで正しく画像信号が受信されなかったときに、正しく受信されなかったフレームが連続したものと見なす。このとき、この所定時間を、例えば４秒間とすることで、約２８フレームの画像信号が正しく受信されなかったこととなる。
【００１３】
又、前記エラーチェック部において、前記モデムで正しく受信されなかったフレームが連続したことが確認されると、前記モデムの通信動作を前記第２状態に切り換えた後、前記通信相手となるファクシミリ装置から信号を受信したとき、前記通信相手となるファクシミリ装置に対して、正しく受信されなかったフレームから、前記モデムが前記第１状態で受信するであろう最後のフレームまでの画像信号の再送を求めるためのＰＰＲを送信するようにすることで、エラーの発生が開始したフレーム以降の全てのフレームについての画像信号の再送を求めることができる。
【００１４】
又、前記エラーチェック部において、前記モデムで正しく受信されなかったフレームが連続したことが確認されると、前記モデムの通信動作を前記第２状態に切り換えた後、前記通信相手となるファクシミリ装置から信号を受信するために、前記モデムが前記第１状態で受信する画像信号の最大フレーム数に応じた時間、前記モデムを前記第２状態で待機させるようにすることで、画像信号の最初のフレームからエラーが発生して画像信号が全て受信不可能であるときも、ＰＰＳを受信可能な状態とすることができる。尚、第１状態で受信する画像信号の最大フレーム数に応じた時間は、画像信号の各フレーム間のフラグに対する時間を省いたものとしても構わない。
【００１５】
本発明のファクシミリ通信方法は、他のファクシミリ装置と送受信を行うモデムを有し、該モデムで受信した画像信号をフレーム毎に正しく受信されたか否かの確認を行い、正しく受信されなかったフレームが確認されたとき、通信相手となるファクシミリ装置に対して正しく受信されなかったフレームの画像信号の再送を求めるためのＥＣＭ機能を備えたファクシミリ装置におけるファクシミリ通信方法において、所定時間、前記モデムで正しく画像信号が受信されなかったときに、正しく受信されなかったフレームが連続したものと見なすとともに、正しく受信されなかったフレームが連続したことが確認されると、前記モデムの通信動作を、第１通信速度で送受信される画像信号を受信する第１状態から、第２通信速度で送受信される画像信号を受信する第２状態に強制的に切り換えることを特徴とする。
【００１７】
又、前記モデムで正しく受信されなかったフレームが連続したことが確認されると、前記モデムの通信動作を前記第２状態に切り換えた後、前記通信相手となるファクシミリ装置から信号を受信したとき、前記通信相手となるファクシミリ装置に対して、正しく受信されなかったフレームから、前記モデムが前記第１状態で受信するであろう最後のフレームまでの画像信号の再送を求めるためのＰＰＲを送信するようにすることで、受信しなかったフレームの画像信号の再送要求を行うことができる。
【００１８】
又、前記モデムで正しく受信されなかったフレームが連続したことが確認されると、前記モデムの通信動作を前記第２状態に切り換えた後、前記通信相手となるファクシミリ装置から信号を受信するために、前記モデムが前記第１状態で受信する画像信号の最大フレーム数に応じた時間、前記モデムが前記第２状態で待機するようにしても構わない。
【００１９】
【発明の実施の形態】
本発明の実施形態について、図面を参照して説明する。図１は、本実施形態のファクシミリ装置の内部構成を示すブロック図である。図２は、図１のファクシミリ装置の動作を示すフローチャートである。
【００２０】
図１のファクシミリ装置は、装置全体の制御を行う主制御部１と、画像データの符号化を行う符号化部２と、受信信号の復号化を行う復号化部３と、信号の変復調を行うモデム４と、ファクシミリと電話との間での電話回線との接続の切り換えを行うＮＣＵ（ＮｅｔｗｏｒｋＣｏｎｔｒｏｌＵｎｉｔ）５と、送信原稿の内容を読み取るためのＣＣＤ（ＣｈａｒｇｅＣｏｕｐｌｅｄＤｅｖｉｃｅ）センサなどの光電変換素子で構成される画像読み取り部６と、画像読み取り部６で得られた電気信号による画像データに対してシェーディング補正や二値化処理又はハーフトーン処理などの画像処理を行う画像処理部７と、復号化された画像データに対してスムージング処理などの画像処理を行う記録処理部８と、記録処理部８で画像処理された画像データに従って記録紙に受信原稿の印字を行うとともに印字された記録紙を排出する出力部９と、送受信の指示などを行うための操作部１０と、相手先電話番号などを表示するための表示部１１と、相手先番号などを格納するためのメモリ１２と、受信原稿の画像データを格納するための画像メモリ１３とを備える。
【００２１】
このような構成のファクシミリ装置は、図３のように通信を行う。即ち、送信側のファクシミリ装置の操作部１０が操作されて、相手先電話番号がダイヤルされると、発呼動作が行われて、相手の読み出しを行うためにＣＮＧ（ＣａｌｌｉｎｇＴｏｎｅ）がモデム４及びＮＣＵ５を通じて送信される。受信側のファクシミリ装置のＮＣＵ５でＣＮＧを受信すると、ファクシミリ通信が行われることが認識される。そして、受信側のファクシミリ装置が、ＣＥＤ（ＣａｌｌｅｄＴｏｎｅ）をモデム４及びＮＣＵ５を通じて送信側のファクシミリ装置に送信する。尚、ＣＮＧ及びＣＥＤによって、送信側及び受信側それぞれがファクシミリ装置であることが識別される。
【００２２】
このようにしてフェーズＡの動作が行われて、送信側と受信側のファクシミリ装置の間で通信接続が成されると、受信側のファクシミリ装置から、ＮＳＦ（Ｎｏｎ−ＳｔａｎｄａｒｄＦａｃｉｌｉｔｉｅｓ）、ＣＳＩ（ＣａｌｌｅｄＳｕｂｓｃｒｉｂｅｒＩｄｅｎｔｉｆｉｃａｔｉｏｎ）、ＤＩＳ（ＤｉｇｉｔａｌＩｄｅｎｔｉｆｉｃａｔｉｏｎＳｉｇｎａｌ）が送信される。このとき、ＮＳＦがメーカ独自のファクシミリ装置の機能を、ＣＳＩが受信側の電話番号を、ＤＩＳがＧ３標準のファクシミリ装置の機能を、それぞれ示す。尚、ファクシミリ装置の機能とは、モデムの種類、送受信する原稿の記録紙幅、通信スピードなどを表す。
【００２３】
これに対して、送信側のファクシミリ装置から、ＮＳＳ（Ｎｏｎ−ＳｔａｎｄａｒｄＦａｃｉｌｉｔｉｅｓＳｅｔ−ｕｐ）、又は、ＴＳＩ（ＴｒａｎｓｍｉｔｔｉｎｇＳｕｂｓｃｒｉｂｅｒＩｄｅｎｔｉｆｉｃａｔｉｏｎ）及びＤＣＳ（ＤｉｇｉｔａｌＣｏｍｍａｎｄＳｉｇｎａｌ）が送信される。このとき、ＮＳＳが設定されたメーカ独自のファクシミリ装置の送信条件を、ＴＳＩが送信側の電話番号を、ＤＣＳが設定されたＧ３標準のファクシミリ装置の送信条件を、それぞれ示す。尚、ＮＳＳ及びＤＣＳは、受信したＮＳＦ及びＤＩＳによって認識した受信側の機能に応じて設定された送信条件を表す。又、ＮＳＳ、ＮＳＦは、送受信のファクシミリ装置が同一メーカのものであるときに、それぞれ認識される信号である。
【００２４】
そして、正常に通信できるかを試験するために、送信側のファクシミリ装置よりＴＣＦ（ＴｒａｉｎｉｎｇＣｈｅｃｋＦｉｅｌｄ）が送信される。このＴＣＦを受信した受信側のファクシミリ装置では、受信したＴＣＦに誤りが確認されなかったとき、正常に送信動作が行われたことを示すＣＦＲ（ＣｏｎｆｉｒｍａｔｉｏｎｔｏＲｅｃｅｉｖｅ）を、送信側のファクシミリ装置に対して送信する。このフェーズＡ及びフェーズＢでは、ファクシミリ装置は、ＦＳＫ信号を通信用の信号として使用するため、モデム４を３００ｂｐｓの送信速度に応じた状態にする。尚、ＴＣＦは、試験用の信号であるため、フェーズＣの画像信号と同じ送信速度で送信される。
【００２５】
このようにしてフェーズＢの通信動作が行われて、送信側のファクシミリ装置が受信側のファクシミリ装置の機能に応じた送信条件で送信するように設定された後、正常に通信が行われることが確認されると、フェーズＣに移行する。このフェーズＣでは、送信側のファクシミリ装置より画像信号が送信信号として受信側のファクシミリ装置に送信される。このとき、受信側のファクシミリ装置は、モデム４を１４４００ｂｐｓの送信速度に応じた状態にする。
【００２６】
このようにしてフェーズＣに、ファクシミリ装置の通信状態が遷移した後の受信側のファクシミリ装置の動作について、図２のフローチャートを参照して説明する。尚、以下において、モデム４の通信動作状態のうち、１４４００ｂｐｓの通信速度の画像信号を送受信するための通信状態のことを「画像信号通信モード」、３００ｂｐｓの通信速度のＦＳＫ信号を送受信するための通信状態のことを「ＦＳＫ通信モード」と呼ぶ。
【００２７】
上述のようにフェーズＢからフェーズＣに通信状態が遷移すると、受信側のファクシミリ装置において、モデム４をＦＳＫ通信モードから画像信号通信モードに切り換える（ＳＴＥＰ１）。このようにモデム４が画像信号通信モードとされた後、送信側のファクシミリ装置から１フレームが２５６バイトの画像信号が送信され、モデム４で受信される（ＳＴＥＰ２）。このとき、受信された画像信号は、モデム４で復調される。この画像信号は、多くのビットデータを送信することが可能な変調方式であるＱＡＭ（ＱｕａｄｒａｔｕｒｅＡｍｐｌｉｔｕｄｅＭｏｄｕｌａｔｉｏｎ）方式やＤＰＳＫ（ＤｉｆｆｅｒｅｎｔＰｈａｓｅＳｈｉｆｔＫｅｙｉｎｇ）方式などで変調が施されている。
【００２８】
このようにモデム４で画像信号を復調したとき、通信エラーが発生したか否かが確認される（ＳＴＥＰ３）。このとき、受信した画像信号にノイズが重畳されているために、モデム４において正常なときのように復調することが不可能な状態となりエラーが発生すると、復号化部３を通じて主制御部１が通信エラーが発生したことを認識される。このような通信エラーを主制御部１が認識しなかったとき（Ｎｏ）、受信した画像信号が復号化部３で復号化された後、ＲＣＰフレームであるか否かが確認される（ＳＴＥＰ４）。
【００２９】
そして、画像信号の受信が開始されてから最終フレームとなるＲＣＰフレームが受信されていることが確認されると（Ｙｅｓ）、このＲＣＰフレームの後に、送信側のファクシミリ装置からＦＳＫ信号であるＰＰＳ−ＥＯＰが送信されるため、モデム４の状態をＦＳＫ通信モードに切り換える（ＳＴＥＰ５）。よって、フェーズＤに通信状態が遷移する。又、ＲＣＰフレームでない場合は（Ｎｏ）、再度、ＳＴＥＰ２以降の動作が行われる。
【００３０】
又、ＳＴＥＰ３において、エラーの発生が確認されると、エラーが所定時間継続して発生するか否かが主制御部１において確認される（ＳＴＥＰ６）。このとき、一時的に発生したエラーである場合は（Ｎｏ）、ＳＴＥＰ４に移行して、ＲＣＰフレームを受信しているか否かの確認が行われる。逆に、エラーが所定時間継続して発生したことが確認されると（Ｙｅｓ）、それ以降もエラーが発生し続けてモデム４での受信信号が発散する可能性が高くなり、ＲＣＰフレームの確認が行われず、ＦＳＫ通信モードへの切り換えが行われない可能性があるため、強制的にＦＳＫ通信モードへ切り換える（ＳＴＥＰ７）。
【００３１】
このＳＴＥＰ６でのエラーの継続を確認するために規定された所定時間は、例えば、４秒程度としても構わない。この４秒間に、４×１４４００＝５７６００ビット、即ち、７２００バイトのデータが受信される。即ち、１フレームが２５６バイトであるので、４秒間に約２８フレームの画像信号が受信されることとなる。よって、フェーズＣに状態が遷移して、最大２５６フレームの画像信号が送受信されることを考慮すると、このように４秒と規定することによって、十分にモデム４が発散したと認識可能な量のエラーが発生しているとすることができる。
【００３２】
このように、モデム４の通信状態をＦＳＫ通信モードへ切り換えると、ＰＰＳ−ＥＯＰの受信が確認される（ＳＴＥＰ８）。このとき、ＰＰＳ−ＥＯＰの受信が確認されると（Ｙｅｓ）、フェーズＤに状態遷移するとともに、ＳＴＥＰ３でエラーが発生したことが検出されたフレーム以降の全フレームの送信を要求するためのＰＰＲを送信する（ＳＴＥＰ９）。
【００３３】
又、ＰＰＳ−ＥＯＰの受信が確認されなかった場合は（Ｎｏ）、モデム４の通信状態をＦＳＫ通信モードに切り換えてから、所定時間が経過したか否かの確認が行われる（ＳＴＥＰ１０）。このとき、所定時間が経過していないときは（Ｎｏ）、再度、ＳＴＥＰ８でＰＰＳ−ＥＯＰの受信が確認される。逆に、所定時間が経過したときは（Ｙｅｓ）、通信エラーとされて、送信側のファクシミリ装置との通信回線を切断する（ＳＴＥＰ１１）。
【００３４】
尚、ＳＴＥＰ１０で確認される所定時間は、次のように規定することができる。フェーズＣに遷移されてから２５６バイトのフレームが最大２５６フレーム分送信されるため、最大２５６×２５６＝６５５３６バイトのデータが、フェーズＣに遷移されてから送信される。よって、通信速度が１４４００ｂｐｓであるため、この最大フレーム分が送信されるときにかかる時間が、６５５３６×８／１４４００＝３６．４秒となる。即ち、ＳＴＥＰ１０で確認される所定時間を最低でも３６．４秒とすればよい。尚、このように算出された所定時間は、フェーズＣで受信される画像信号において、各フレーム間に配置されるフラグについての時間を除いたものであるので、フラグ送出時間を考慮すると、もう少し長くする必要がある。
【００３５】
上述のように、フェーズＣに通信状態が遷移した後、図２のフローチャートに従って、受信側のファクシミリ装置が動作した後、フェーズＤに通信状態が遷移すると、従来の技術で説明したように、受信した画像信号にエラーがある場合は、ＰＰＳ−ＥＯＰを受信すると、図３のように、エラーの発生したフレームの再送を要求するためのＰＰＲが送信側のファクシミリ装置に送信される。このとき、モデム４での受信信号が発散したものと見なされた場合は、上述したように、最初にエラーが発生したことが確認されたフレーム以降の全てのフレームの再送を要求するためのＰＰＲが送信側のファクシミリ装置に送信される。
【００３６】
又、フェーズＤに通信状態が遷移して、受信側のファクシミリ装置が受信した画像信号にエラーがなかった場合は、ＰＰＳ−ＥＯＰを受信すると、図３のようにＭＣＦを送信側のファクシミリ装置に正常に通信が行われたことを通知する。そして、ＭＣＦを受信した送信側のファクシミリ装置がＤＣＮを受信側のファクシミリ装置に送信して、回線を切断する。
【００３７】
尚、本明細書では、説明を簡単にするために、上述したように、画像信号の送信終了後にＰＰＳとともにＥＯＰが送信されるような、最終ページとなる画像信号が送信されたときの動作について説明したが、送信する原稿の途中ページの画像信号が送信されたときの動作についても同様である。即ち、１ブロック又は１ページ分の画像信号が送信された後に、フェーズＤに状態遷移し、送信側のファクシミリ装置からＰＰＳとともにＮＵＬＬ又はＥＯＭ（ＥｎｄＯｆＭｅｓｓａｇｅ）が送信される場合も、ＮＵＬＬが送信されるときは受信側のファクシミリ装置がＭＣＦを送信した後フェーズＣに状態遷移すること以外、又、ＥＯＭが送信されるときは受信側のファクシミリ装置がＭＣＦを送信した後フェーズＢに状態遷移すること以外、同様の動作が行われる。
【００３８】
又、画像信号及びＦＳＫ信号の通信速度をそれぞれ、１４４００ｂｐｓ及び３００ｂｐｓとして説明したが、それぞれの通信速度についてはこれに限るものではない。
【００３９】
【発明の効果】
本発明によると、エラーが連続的に発生して、連続した複数のフレームの画像信号が受信されなくなったとき、モデムの通信状態が強制的に第２状態とされるため、インパルスノイズや瞬断によって、画像信号が受信不可能な状態となっても、ＦＳＫ信号が受信してフェーズＤに状態遷移したことを認識することができる。即ち、ＰＰＳを受信することが可能な状態とすることができる。
【００４０】
又、正しく受信されなかった連続したフレームにおける最初のフレームから、モデムが第１状態で受信するであろう最後のフレームまでの画像信号の再送を求めるためのＰＰＲを送信するので、エラーの発生が開始したフレーム以降の全てのフレームについての画像信号の再送を求めることができる。更に、第１状態であるフェーズＣで受信する画像信号の最大フレーム数に応じた時間、モデムを第２状態に切り換えて待機させるので、画像信号の最初のフレームからエラーが発生して画像信号が全て受信不可能であるときも、ＰＰＳを受信可能な状態とすることができる。
【図面の簡単な説明】
【図１】本発明のファクシミリ装置の内部構成を示すブロック図。
【図２】図１のファクシミリ装置の動作を示すフローチャート。
【図３】ファクシミリ装置の通信動作を示すタイムチャート。
【符号の説明】
１主制御部
２符号化部
３復号化部
４モデム
５ＮＣＵ
６画像読み取り部
７画像処理部
８記録処理部
９出力部
１０操作部
１１表示部
１２メモリ
１３画像メモリ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a facsimile apparatus and a facsimile communication method in which a modulation scheme of a received signal is switched, and particularly to a facsimile apparatus having an ECM (Error Correction Mode) function as an error retransmission method and a facsimile communication method of the facsimile apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a facsimile apparatus, when an image signal was not correctly received on a receiving side due to noise or the like on a telephone line at the time of communication, a request for retransmission of an image signal was made to a transmitting side, and the reception was not performed correctly. It has an ECM function for retransmitting image signals. When communication is performed using this ECM function, as shown in FIG. 3, after transmitting a 256-byte image frame of one frame for 256 frames, the mode is switched to phase D, and PPS-EOP (Partial Page Signal- End of Procedure) is transmitted from the facsimile machine on the transmitting side.
[0003]
The receiving-side facsimile apparatus that has received the PPS-EOP recognizes from the EOP that the transmission of the transmission signal of the last page has ended, and recognizes from the PPS that the communication is ECM communication. At this time, when there is a frame that is not correctly received due to superimposition of noise in the transmitted image signal of 256 frames, as shown in FIG. Partial Page
Request) is transmitted to the transmitting facsimile machine.
[0004]
The transmitting facsimile apparatus that has received the PPR recognizes the frame that was not correctly received by the receiving facsimile apparatus from the PPR, retransmits the image signal of the frame, and then transmits the PPS-EOP. When the receiving-side facsimile apparatus receives the image signal of the retransmitted frame, if there is a frame that was not correctly received, the PPR is transmitted again, and the above-described communication operation is repeated in the receiving-side and transmitting-side facsimile apparatuses. It is.
[0005]
On the other hand, when the image signal is correctly received by the receiving-side facsimile apparatus, an MCF (Message Confirmation) indicating that the image signal has been correctly received is transmitted as shown in FIG. When the transmitting facsimile apparatus receives the MCF and recognizes that the image signal has been correctly received, as shown in FIG. 3, the receiving side facsimile apparatus transmits a DCN (Disconnect) signal to disconnect the line. Inform the device.
[0006]
As described above, when facsimile communication is performed using the ECM function, an image signal of a frame that has not been correctly received is retransmitted until it is correctly received, so that the image signal is reliably transmitted to the receiving facsimile apparatus. can do.
[0007]
[Problems to be solved by the invention]
However, if the noise superimposed on the transmitted image signal is temporary and an error occurs intermittently, the error can be dealt with by the ECM function. If this occurs and the received signal from the modem provided in the facsimile apparatus diverges, the RCP (Return to Control Partial) frame, which is the last frame of the image signal, cannot be detected, and PPS-EOP cannot be detected. Sometimes. This is because the PPS-EOP is transmitted at a communication speed of 300 bps while the image signal is transmitted at a communication speed of 14400 bps, and the PPS-EOP is transmitted after the reception of the image signal. This is because it is necessary to switch the reception mode of the modem in order to receive the message.
[0008]
That is, when an image signal is received in a receiving state corresponding to a communication speed of 14400 bps and a normal operation is performed, the receiving state is switched to a receiving state corresponding to a communication speed of 300 bps after detecting an RCP frame. If an error occurs continuously during reception, the RCP frame cannot be detected, so that the reception state cannot be switched and the reception of the PPS-EOP cannot be confirmed. Therefore, the PPR cannot be transmitted from the facsimile machine on the receiving side, and a request for retransmission cannot be made. Note that signals transmitted and received at a communication speed of 300 bps in Phase B and Phase D, such as PPS-EOP and PPR, are referred to as FSK (Frequency Shift Keying) signals.
[0009]
In view of such a problem, the present invention provides a facsimile apparatus and a facsimile communication method capable of reliably receiving a partial page signal (PPS) when performing a communication operation using an ECM function. The purpose is to:
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a facsimile apparatus of the present invention includes a modem for transmitting / receiving a signal to / from another facsimile apparatus, and an error check unit for confirming whether or not a received image signal is correctly received for each frame. And an ECM function for requesting a facsimile machine as a communication partner to retransmit an image signal of a frame that was not correctly received when a frame that was not correctly received by the modem was confirmed by the error check unit. In the facsimile apparatus having the above, in the error check unit, when the image signal is not correctly received by the modem for a predetermined time, the frame that is not correctly received is regarded as a continuous frame, and the frame is correctly received by the modem. If it is confirmed that the missing frames are continuous, The signal operation, from a first state for receiving an image signal transmitted and received first communication speed, and wherein the forcibly switches it to a second state for receiving image signals transmitted and received at a second communication speed.
[0011]
In such a facsimile apparatus, when an error check unit continuously detects frames that are not correctly received and in which an error occurs, the facsimile apparatus receives an image signal having a high communication speed such as 14400 bps. The first state is switched to the second state in which an FSK signal having a low communication speed such as 300 bps is received. By doing so, when the modem enters a divergent state in which the image signal cannot be received normally, it is possible to receive the FSK signal even if it is impossible to detect the RCP frame which is the last frame of the image signal. Therefore, it is possible to recognize that the communication state of the facsimile machine as the communication partner has shifted to phase D.
[0012]
In such a facsimile apparatus , when the modem does not correctly receive an image signal for a predetermined time in the error check unit, it is considered that frames that were not correctly received are continuous . At this time, by setting the predetermined time to, for example, 4 seconds, it means that the image signal of about 28 frames was not correctly received.
[0013]
Further, in the error checking unit, when it is confirmed that the frames that have not been correctly received by the modem continue, the communication operation of the modem is switched to the second state, and then the facsimile apparatus as the communication partner is switched. When receiving a signal, the facsimile machine of the communication partner requests retransmission of an image signal from a frame that is not received correctly to a last frame that the modem will receive in the first state. By transmitting the PPR, it is possible to request retransmission of image signals for all frames after the frame where the occurrence of the error has started.
[0014]
Further, in the error checking unit, when it is confirmed that the frames that have not been correctly received by the modem continue, the communication operation of the modem is switched to the second state, and then the facsimile apparatus as the communication partner is switched. In order to receive the signal, the modem is caused to wait in the second state for a time corresponding to the maximum number of frames of the image signal received by the modem in the first state, so that the first frame of the image signal is received. Also, when an error has occurred and all image signals cannot be received, the PPS can be placed in a receivable state. The time corresponding to the maximum number of frames of the image signal received in the first state may be such that the time for the flag between the frames of the image signal is omitted.
[0015]
The facsimile communication method of the present invention has a modem for transmitting and receiving to and from another facsimile machine, and confirms whether or not an image signal received by the modem is correctly received for each frame. When confirmed, in a facsimile communication method in a facsimile apparatus having an ECM function for requesting a retransmission of an image signal of a frame that has not been correctly received to a facsimile apparatus as a communication partner, the image is correctly transmitted by the modem for a predetermined time. When a signal is not received, it is considered that frames that have not been received correctly are continuous, and when it is confirmed that frames that have not been received correctly are continuous, the communication operation of the modem is performed at a first communication speed. in the first state for receiving an image signal to be transmitted and received, it is transmitted and received at a second communication speed Wherein the forced switch it to the second state for receiving an image signal.
[0017]
Further, when it is confirmed that the frames not correctly received by the modem are continuous, after switching the communication operation of the modem to the second state, when a signal is received from the facsimile machine as the communication partner, A PPR for requesting a retransmission of an image signal from a frame that is not received correctly to a last frame that the modem will receive in the first state is transmitted to the facsimile apparatus that is the communication partner. By doing so, it is possible to request retransmission of the image signal of the frame not received.
[0018]
Further, when it is confirmed that the frames not correctly received by the modem are continuous, after switching the communication operation of the modem to the second state, it is necessary to receive a signal from the facsimile apparatus as the communication partner. Alternatively, the modem may wait in the second state for a time corresponding to the maximum number of frames of the image signal received by the modem in the first state.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the internal configuration of the facsimile apparatus of the present embodiment. FIG. 2 is a flowchart showing the operation of the facsimile machine of FIG.
[0020]
The facsimile apparatus of FIG. 1 performs a main control unit 1 that controls the entire apparatus, an encoding unit 2 that encodes image data, a decoding unit 3 that decodes a received signal, and modulates and demodulates a signal. A modem 4, an NCU (Network Control Unit) 5 for switching connection between a facsimile machine and a telephone line, and a photoelectric conversion element such as a CCD (Charge Coupled Device) sensor for reading the contents of a transmission original. And an image processing unit 7 that performs image processing such as shading correction, binarization processing, or halftone processing on image data based on the electric signal obtained by the image reading unit 6, and decoding. A recording processing unit 8 that performs image processing such as smoothing processing on the converted image data, and An output unit 9 for printing a received document on a recording sheet according to image data and discharging the printed recording sheet, an operation unit 10 for giving a transmission / reception instruction and the like, and a display for displaying a destination telephone number and the like The image processing apparatus includes a unit 11, a memory 12 for storing a destination number, and the like, and an image memory 13 for storing image data of a received document.
[0021]
The facsimile apparatus having such a configuration performs communication as shown in FIG. That is, when the operation unit 10 of the facsimile apparatus on the transmitting side is operated and the telephone number of the other party is dialed, a calling operation is performed, and the CNG (Calling Tone) is connected to the modem 4 and the modem 4 to read out the other party. Sent through NCU5. When CNG is received by the NCU 5 of the facsimile machine on the receiving side, it is recognized that facsimile communication is performed. Then, the receiving-side facsimile apparatus transmits the CED (Called Tone) to the transmitting-side facsimile apparatus through the modem 4 and the NCU 5. It should be noted that the transmission side and the reception side are each identified as a facsimile apparatus by CNG and CED.
[0022]
When the operation of the phase A is performed as described above and a communication connection is established between the transmitting side and the receiving side facsimile apparatus, the receiving side facsimile apparatus transmits NSF (Non-Standard Facilities) and CSI (Called). A Subscriber Identification (DIS) and a Digital Identification Signal (DIS) are transmitted. At this time, NSF indicates the function of the facsimile machine unique to the manufacturer, CSI indicates the telephone number of the receiving side, and DIS indicates the function of the G3 standard facsimile machine. The function of the facsimile apparatus indicates the type of modem, the recording paper width of a document to be transmitted / received, the communication speed, and the like.
[0023]
On the other hand, the facsimile apparatus on the transmitting side transmits NSS (Non-Standard Facilities Set-up), or TSI (Transmitting Subscriber Identification) and DCS (Digital Command Signal). At this time, the transmission conditions of the facsimile machine unique to the maker in which the NSS is set, the TSI indicates the telephone number of the transmitting side, and the transmission conditions of the G3 standard facsimile apparatus in which the DCS is set. Note that NSS and DCS represent transmission conditions set according to the function of the receiving side recognized by the received NSF and DIS. NSS and NSF are signals recognized when the transmitting and receiving facsimile apparatuses are of the same manufacturer.
[0024]
Then, a TCF (Training Check Field) is transmitted from the facsimile machine on the transmission side in order to test whether communication can be performed normally. When no error is confirmed in the received TCF, the receiving-side facsimile apparatus that has received the TCF sends a CFR (Confirmation to Receive) indicating that the transmission operation has been normally performed to the transmitting-side facsimile apparatus. To send. In the phase A and the phase B, the facsimile apparatus uses the FSK signal as a signal for communication, and sets the modem 4 to a state corresponding to a transmission speed of 300 bps. Since the TCF is a test signal, it is transmitted at the same transmission speed as the phase C image signal.
[0025]
In this way, the communication operation of the phase B is performed, and after the transmission-side facsimile apparatus is set to transmit under the transmission condition according to the function of the reception-side facsimile apparatus, normal communication may be performed. If confirmed, the process proceeds to phase C. In this phase C, the image signal is transmitted from the transmission-side facsimile apparatus to the reception-side facsimile apparatus as a transmission signal. At this time, the facsimile machine on the receiving side sets the modem 4 in a state corresponding to the transmission speed of 14400 bps.
[0026]
The operation of the receiving-side facsimile apparatus after the communication state of the facsimile apparatus has shifted to phase C in this manner will be described with reference to the flowchart in FIG. In the following, among the communication operation states of the modem 4, a communication state for transmitting and receiving an image signal at a communication speed of 14400 bps is referred to as an "image signal communication mode", and a communication state for transmitting and receiving an FSK signal at a communication speed of 300 bps. The communication state is called "FSK communication mode".
[0027]
When the communication state transitions from phase B to phase C as described above, the facsimile machine on the receiving side switches the modem 4 from the FSK communication mode to the image signal communication mode (STEP 1). After the modem 4 is set to the image signal communication mode in this way, an image signal of 256 bytes in one frame is transmitted from the facsimile apparatus on the transmitting side and received by the modem 4 (STEP 2). At this time, the received image signal is demodulated by the modem 4. This image signal is modulated by a QAM (Quadrature Amplitude Modulation) method or a DPSK (Differential Phase Shift Keying) method which is a modulation method capable of transmitting a large amount of bit data.
[0028]
As described above, when the image signal is demodulated by the modem 4, it is confirmed whether or not a communication error has occurred (STEP 3). At this time, since noise is superimposed on the received image signal, demodulation cannot be performed as in the normal case in the modem 4 and an error occurs. It is recognized that a communication error has occurred. When such a communication error is not recognized by the main control unit 1 (No), after the received image signal is decoded by the decoding unit 3, it is confirmed whether or not the received image signal is an RCP frame (STEP 4). .
[0029]
Then, if it is confirmed that the RCP frame which is the last frame has been received after the start of the reception of the image signal (Yes), after this RCP frame, the facsimile apparatus on the transmitting side transmits the PPS-frame which is the FSK signal. Since the EOP is transmitted, the state of the modem 4 is switched to the FSK communication mode (STEP 5). Therefore, the communication state transitions to phase D. If the frame is not an RCP frame (No), the operation after STEP 2 is performed again.
[0030]
When the occurrence of an error is confirmed in STEP 3, the main control unit 1 confirms whether or not the error continues for a predetermined time (STEP 6). At this time, if the error has occurred temporarily (No), the process proceeds to STEP 4 to check whether an RCP frame has been received. Conversely, if it is confirmed that the error has continued for a predetermined period of time (Yes), there is a high possibility that the error will continue to occur and the received signal from the modem 4 will diverge, and the RCP frame is confirmed. Is not performed, and there is a possibility that switching to the FSK communication mode is not performed. Therefore, the mode is forcibly switched to the FSK communication mode (STEP 7).
[0031]
The predetermined time specified for confirming the continuation of the error in STEP 6 may be, for example, about 4 seconds. In these four seconds, 4 × 14400 = 57600 bits, that is, 7,200 bytes of data are received. That is, since one frame is 256 bytes, an image signal of about 28 frames is received in 4 seconds. Therefore, considering that the state transits to the phase C and the image signal of a maximum of 256 frames is transmitted and received, by defining the time as 4 seconds in this way, the amount of the modem 4 that can be recognized as sufficiently diverged can be recognized. It can be assumed that an error has occurred.
[0032]
Thus, when the communication state of the modem 4 is switched to the FSK communication mode, the reception of the PPS-EOP is confirmed (STEP 8). At this time, if the reception of the PPS-EOP is confirmed (Yes), the state transits to the phase D, and the PPR for requesting the transmission of all frames after the frame in which the error is detected in STEP 3 is transmitted. Transmit (STEP 9).
[0033]
If the reception of the PPS-EOP is not confirmed (No), it is confirmed whether or not a predetermined time has elapsed since the communication state of the modem 4 is switched to the FSK communication mode (STEP 10). At this time, if the predetermined time has not elapsed (No), the reception of the PPS-EOP is confirmed again in STEP8. Conversely, when the predetermined time has elapsed (Yes), a communication error is determined, and the communication line with the facsimile machine on the transmitting side is disconnected (STEP 11).
[0034]
Note that the predetermined time confirmed in STEP 10 can be defined as follows. Since a 256-byte frame is transmitted for a maximum of 256 frames after the transition to the phase C, data of a maximum of 256 × 256 = 65536 bytes is transmitted after the transition to the phase C. Therefore, since the communication speed is 14400 bps, the time taken to transmit this maximum frame is 65536 × 8/14400 = 36.4 seconds. That is, the predetermined time confirmed in STEP 10 should be at least 36.4 seconds. Note that the predetermined time calculated in this manner excludes the time for the flag arranged between the frames in the image signal received in the phase C. Therefore, considering the flag transmission time, the predetermined time is a little longer. There is a need to.
[0035]
As described above, after the communication state transitions to phase C, the communication state transitions to phase D after the reception-side facsimile apparatus operates according to the flowchart of FIG. When the PPS-EOP is received when there is an error in the transmitted image signal, as shown in FIG. 3, a PPR for requesting retransmission of the frame in which the error has occurred is transmitted to the facsimile apparatus on the transmission side. At this time, if it is considered that the received signal from the modem 4 has diverged, as described above, the PPR for requesting retransmission of all frames after the first frame in which an error has been confirmed is generated. Is transmitted to the transmitting facsimile machine.
[0036]
Also, if the communication state transitions to phase D and there is no error in the image signal received by the receiving facsimile apparatus, when the PPS-EOP is received, the MCF is transmitted to the transmitting facsimile apparatus as shown in FIG. Notifies that communication has been performed normally. Then, the transmitting facsimile apparatus receiving the MCF transmits the DCN to the receiving facsimile apparatus and disconnects the line.
[0037]
In this specification, for simplicity of description, as described above, an operation when an image signal to be the last page is transmitted, such as an EOP transmitted together with a PPS after the image signal transmission is completed. As described above, the same applies to the operation when the image signal of the middle page of the original to be transmitted is transmitted. That is, after the image signal for one block or one page is transmitted, the state transitions to phase D, and NULL is transmitted even when NULL or EOM (End Of Message) is transmitted together with PPS from the facsimile machine on the transmission side. When the receiving facsimile machine transmits MCF, the receiving facsimile apparatus changes state to phase C after transmitting the MCF. When the EOM is transmitted, the receiving facsimile apparatus transmits MCF to change the state to phase B. Other than that, a similar operation is performed.
[0038]
Also, the communication speeds of the image signal and the FSK signal are described as 14400 bps and 300 bps, respectively, but the communication speeds are not limited to these.
[0039]
【The invention's effect】
According to the present invention, when errors occur continuously and image signals of a plurality of continuous frames are not received, the communication state of the modem is forcibly set to the second state, so that impulse noise and instantaneous interruption are caused. Thus, even if the image signal cannot be received, it is possible to recognize that the FSK signal has been received and the state has transitioned to phase D. That is, a state where PPS can be received can be set.
[0040]
In addition, since the PPR is transmitted to request retransmission of the image signal from the first frame in the consecutive frames that are not received correctly to the last frame that the modem will receive in the first state, an error occurs. It is possible to request retransmission of image signals for all frames after the start frame. Further, since the modem is switched to the second state and waits for a time corresponding to the maximum number of frames of the image signal received in the phase C which is the first state, an error occurs from the first frame of the image signal and the image signal is generated. Even when all the signals cannot be received, the PPS can be set in a receivable state.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an internal configuration of a facsimile apparatus of the present invention.
FIG. 2 is a flowchart showing the operation of the facsimile apparatus of FIG.
FIG. 3 is a time chart showing a communication operation of the facsimile apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Main control part 2 Encoding part 3 Decoding part 4 Modem 5 NCU
6 Image reading section 7 Image processing section 8 Recording processing section 9 Output section 10 Operation section 11 Display section 12 Memory 13 Image memory

Claims

A modem for transmitting and receiving signals to and from another facsimile apparatus, and an error check unit for checking whether or not the received image signal has been correctly received for each frame, and the frame that has not been correctly received by the modem is In a facsimile apparatus having an ECM (Error Correction Mode) function for requesting a communication partner facsimile apparatus to retransmit an image signal of a frame that has not been correctly received when the error check unit confirms the error,
In the error checking unit, when the image signal is not correctly received by the modem for a predetermined time, the frame that is not correctly received is considered to be continuous, and the frame that is not correctly received by the modem is continuous. Is confirmed,
The communication operation of the modem is forcibly switched from a first state for receiving an image signal transmitted and received at a first communication speed to a second state for receiving an image signal transmitted and received at a second communication speed. Facsimile machine.

A modem for transmitting and receiving signals to and from another facsimile machine, and an error check unit for checking whether or not the received image signal has been correctly received for each frame, and the frame that has not been correctly received by the modem is When the error check unit confirms the ECM (ECM) for requesting the facsimile machine of the communication partner to retransmit the image signal of the frame that was not correctly received. Error Correction Mode ) In a facsimile machine with a function,
  In the error check unit, when it is confirmed that the frame that was not correctly received by the modem is continuous,
  After forcibly switching the communication operation of the modem from a first state of receiving an image signal transmitted and received at a first communication speed to a second state of receiving an image signal transmitted and received at a second communication speed,
  In order to receive a signal from a facsimile apparatus that is the communication partner, the modem waits in the second state for a time corresponding to the maximum number of frames of the image signal received by the modem in the first state. Facsimile machine.

In the error check unit, when it is confirmed that the frame that was not correctly received by the modem is continuous,
After switching the communication operation of the modem to the second state, when a signal is received from the facsimile machine as the communication partner, the modem receives the signal from the facsimile machine as the communication partner. The facsimile apparatus according to claim 1 or 2, wherein the transmitting unit transmits a PPR (Partial Page Request) for requesting retransmission of an image signal up to the last frame that will be received in the first state. .

In the error check unit, when it is confirmed that the frame that was not correctly received by the modem is continuous,
After switching the communication operation of the modem to the second state, a time corresponding to the maximum number of frames of the image signal received by the modem in the first state, in order to receive a signal from the facsimile apparatus as the communication partner. the facsimile apparatus according to claim 1 or claim 3, characterized in that to wait for the modem in the second state.

It has a modem that performs transmission and reception with other facsimile devices, and checks whether or not the image signal received by the modem has been correctly received for each frame. A facsimile communication method in a facsimile apparatus having an ECM function for requesting a facsimile apparatus to retransmit an image signal of a frame that has not been correctly received,
For a predetermined period of time, when the image signal is not correctly received by the modem, it is considered that the incorrectly received frame is continuous,
When it is confirmed that frames that have not been received correctly continue,
The communication operation of the modem is forcibly switched from a first state for receiving an image signal transmitted and received at a first communication speed to a second state for receiving an image signal transmitted and received at a second communication speed. Facsimile communication method.

It has a modem that transmits and receives to and from another facsimile machine, and checks whether or not the image signal received by the modem is correctly received for each frame. A facsimile communication method in a facsimile apparatus having an ECM function for requesting a facsimile apparatus to retransmit an image signal of a frame that has not been correctly received,
  If it is confirmed that frames that were not received correctly are continuous,
  After forcibly switching the communication operation of the modem from a first state of receiving an image signal transmitted and received at a first communication speed to a second state of receiving an image signal transmitted and received at a second communication speed,
  The modem waits in the second state for a time corresponding to the maximum number of frames of the image signal received by the modem in the first state in order to receive a signal from the facsimile apparatus to be the communication partner. Facsimile communication method.

When it is confirmed that the frames that were not correctly received by the modem are continuous,
After switching the communication operation of the modem to the second state, when a signal is received from the facsimile machine as the communication partner, the modem receives the signal from the facsimile machine as the communication partner. 7. The facsimile communication method according to claim 5, further comprising transmitting a PPR for requesting retransmission of an image signal up to a last frame that will be received in the first state. 8.

When it is confirmed that the frames that were not correctly received by the modem are continuous,
After switching the communication operation of the modem to the second state, a time corresponding to the maximum number of frames of the image signal received by the modem in the first state, in order to receive a signal from the facsimile apparatus as the communication partner. facsimile communication method according to claim 5 or claim 7 wherein the modem is characterized in that it waits in the second state.

A transmission / reception unit for transmitting / receiving a signal to / from another communication device, and an error check unit for confirming whether or not the received signal has been correctly received for each predetermined data amount, and the reception / reception unit did not correctly receive When the signal is confirmed by the error check unit, in a communication device having an error correction function for requesting retransmission of a signal that has not been correctly received for a communication device that is a communication partner,
In the error checking unit, for a predetermined time, when the signal is not correctly received by the transmitting and receiving unit, it is considered that the signal of the predetermined data amount is not continuously received correctly, and the predetermined data is received by the transmitting and receiving unit. Once it is determined that the volume of the signal has not been received correctly in succession,
The communication operation of the transmission / reception unit is forcibly switched from a first state for receiving a signal transmitted / received at a first communication rate to a second state for receiving a signal transmitted / received at a second communication rate. Communication device.

A transmission / reception unit for transmitting / receiving signals to / from another communication device, and an error check unit for confirming whether or not the received signal has been correctly received for each predetermined data amount, and the transmission / reception branch unit has not correctly received the signal. When the signal is confirmed by the error check unit, in a communication device having an error correction function for requesting retransmission of a signal that has not been correctly received for a communication device that is a communication partner,
  In the error check unit, when it is confirmed that the signal of the predetermined data amount is not continuously received correctly in the transmission and reception unit,
  After forcibly switching the communication operation of the transmitting / receiving unit from a first state for receiving a signal transmitted / received at a first communication rate to a second state for receiving a signal transmitted / received at a second communication rate,
  In order to receive a signal from a communication device that is the communication partner, the transmitting / receiving unit waits in the second state for a time corresponding to a maximum data amount of a signal received by the transmitting / receiving unit in the first state. Communication device.

It has a transmission / reception unit for transmitting / receiving to / from another communication device, and confirms whether or not the signal received by the transmission / reception unit is correctly received for each predetermined data amount. When a signal is confirmed, a communication method in a communication device having an error correction function for requesting retransmission of a signal that has not been correctly received for a communication device serving as a communication partner,
  For a predetermined time, when the signal is not correctly received by the transmission and reception unit, while assuming that the signal of the predetermined data amount has not been continuously and correctly received,
  When it is confirmed that the signal of the predetermined data amount has not been continuously and correctly received,
  The communication operation of the transmission / reception unit is forcibly switched from a first state for receiving a signal transmitted / received at a first communication rate to a second state for receiving a signal transmitted / received at a second communication rate. Communication method.

It has a transmitting and receiving unit that performs transmission and reception with other communication devices, and checks whether a signal received by the transmitting and receiving unit is correctly received for each predetermined data amount, and when a signal that is not correctly received is confirmed, A communication method in a communication device having an error correction function for requesting retransmission of a signal that has not been correctly received for a communication device serving as a communication partner,
  When it is confirmed that the signal of the predetermined data amount has not been continuously and correctly received,
  After forcibly switching the communication operation of the transmitting / receiving unit from the first state of receiving an image signal transmitted / received at the first communication speed to the second state of receiving a signal transmitted / received at the second communication speed,
  The transmission / reception unit waits in the second state for a time corresponding to a maximum data amount of an image received by the transmission / reception unit in the first state in order to receive a signal from the communication device serving as the communication partner. Communication method.