1. Technical Field
The present invention relates to a data communication and image process system, and more particularly to a device for controlling data transmission/reception between electrophotographic printers from local and remote areas and a method thereof.
2. Background Art
Laser printers or LED (light emitted diode) printers for printing images or documents in response to the reception of signals from a personal computer (hereinafter, referred to as a computer) are well known. In a typical printer of this type as illustrated in U.S. Pat. No. 5,197,117 for Text Information Processing Apparatus Having Printer And Printing Dot Signal Generating Apparatus For The Same issued to Kato et al., a memory is provided for storing image signals from the computer. The computer formats the image signals in the manner required for the printer, and the printer memory is adapted to store bit mapped image pages of images prior to initiating printing. The printer then sequentially reads out from the bit mapped memory to modulate the light beam of a laser diode. The light beam of the laser diode is controlled to scan a photoconductive drum where the image is subsequently stored, developed and transferred to a recording paper in a manner conventional to electrophotographic devices.
This type of printers is different from the general printer in that it employs electrophotographic process to form images with low noise and high resolution. Such printers, however, can only function when they are directly connected to a host computer (i.e., local computer). Consequently, in order for this type of printer to communicate with a remote facility, such as a remote computer or a remote facsimile (FAX) machine via a public subscriber telephone network (PSTN), a separate facsimile machine is required as shown, for example, in U.S. Pat. No. 4,930,017 for Communication Terminal Device issued to Izawa. In Izawa '017, the separate facsimile machine is connected to the laser printer for enabling the laser printer to print facsimile information from a remote facsimile machine, or to scan the information printed on a recording paper and transmit it to a remote facsimile machine via telephone lines of the public subscriber telephone network. However, the information in a computer cannot be directly transmitted to a remote facsimile machine, unless the computer is connected to the cable of the public subscriber telephone network via an interface. The information must be first printed out on a recording paper and then scanned by a host facsimile machine and transmitted to the remote facsimile machine. Likewise, any information from a remote facsimile machine can not be directly displayed by the computer unless the computer is connected on line with the public subscriber telephone network, and must be first received and printed out by the host facsimile machine and then input into the computer. The printing and scanning procedures, however, inevitably delay the time of data transmission, and considerably increase the distortion of the transmitted information.
In Izawa '017, the separate facsimile machine used is of the general type; one that prints facsimile information on a thermosensitive recording paper having a predetermined size. Although this type of facsimile machine is most commonly used, the thermosensitive recording paper is subject to gradual image deterioration over a long period of time. In addition, the thermosensitive recording paper has smooth surface which does not receive and accommodate handwritten characters well. Moreover, the general facsimile machine is limited to operation only with the thermosensitive recording paper having a predetermined size. Consequently, the general facsimile machine is less desirable.
There are two other types of facsimile machines, however. The first type is a PP-facsimile (plain paper facsimile) machine; one that prints facsimile information on a plain, ordinary recording paper rather than printing on a thermosensitive recording paper. The second type is a PC-facsimile (personal computer facsimile) machine; one that is incorporated into a computer to provide the computer with the function of a facsimile machine by way of a facsimile transmission/reception board. In the PP-facsimile machine, the electrophotographic process is employed to form facsimile messages on a plain, ordinary recording paper. Consequently, the facsimile information formed on the recording paper has high resolution and low noise. Although the PP-facsimile machine produces facsimile messages of high resolution, it, however, requires a separate scanner for scanning and reading facsimile information formed on the recording paper if transmission to a remote facsimile machine via the public subscriber telephone network is requested. Unfortunately, if a separate scanner is installed in conjunction with the PP-facsimile machine, the cost of the PP-facsimile machine would exceed the cost of a laser printer. Moreover, the PP-facsimile machine does not have the capability to receive and print image signals from a host computer when compared with the laser printer. Further, when the scanner is used to scan and read facsimile information formed on the recording paper so as to transmit the read facsimile information to a remote facsimile machine via the public subscriber telephone network, data distortion often occurs while driven by the of the scanner. This results in the degradation of the printed facsimile messages at the receiving end of the remote facsimile machine.
The PC-facsimile machine, on the other hand, uses a computer to transmit a screen edited by the computer to the remote facility, such as a remote facsimile machine or a remote computer in the form of an image file. When serving as a facsimile machine, the computer must, however, be used in conjunction with a scanner as an input device and a printer as an output device. Any facsimile information received from the remote facility such as a remote facsimile machine is converted into a language readable by the computer and is stored in its auxiliary memory in the form of the image file for subsequent display on its monitor, or print out by the printer. The PC-facsimile has an enormous advantage in that the document transmitted via the public subscriber telephone network is quite clean except for a few errors occur during the transmission, when compared with both the general facsimile and PP-facsimile machines where most of the errors are generated when the scanner scans the document. As mentioned earlier, in order to implement the PC-facsimile, a facsimile transmission/reception board is built-in the PC as shown in U.S. Pat. No. 5,196,943 for Facsimile Information Distribution Apparatus issued to Hersee.
A typical PC-facsimile machine is shown in U.S. Pat. No. 5,228,128 for Personal Computer Facsimile Device issued to Kim, and assigned to the same assignee of this application. In Kim '128, the PC-facsimile machine is designed to, inter alia, transmit a document or an image directly to and receive the same directly from a remote facsimile machine via the public subscriber telephone network. The remote facsimile machine in Kim '128 can be another PC-facsimile machine or a general facsimile or PP-Facsimile machine. In order for the PC-facsimile to communicate with the remote general facsimile, these machines must first convert the image file being transmitted from a standard computer file format, such as ASCII, into a graphical image format compatible with the remote facsimile machine and transmit such graphical image to the remote facsimile machine. Since graphical images arc much larger than standard files, the conversion requires significantly more time to print a file remotely. Also, if the remote receiving facsimile machine is also a PC-Facsimile, the file may be stored in an auxiliary memory and a user of the remote receiving facsimile machine must intervene to print the file before it is available.
To avoid the time delay conversion of a standard computer file format into a graphical image format and the user intervention, U.S. Pat. No. 5,175,762 for Remote Printing Using Facsimile issued to Kochis et al. is disclosed to reduce the printing time. The PC-facsimile of Kochis et al. '762 as well as other conventional PC-facsimiles, however, require a separate printer for output purposes; that is, a separate high resolution printer must be connected to the computer in order to observe the document on a recording paper. Moreover, in order for the PC-facsimile to receive the facsimile information transmitted via the public subscriber telephone network, the computer must always be turned on. If, for any reasons, the computer is turned off, the facsimile information transmitted cannot be received. If, the remote computer is turned on, however, its auxiliary memory is prone to receive facsimile information indiscriminately from several facsimile sources which could overload its memory capacity and possibly deny reception of potentially important facsimile information. Further, in the conventional PC-facsimile, when the computer receives or transmits the facsimile information from or to the remote facsimile machine, it typically cannot process other functions. Consequently, the user would have to wait for the computer to complete the reception or transmission of the facsimile information before he could proceed to use other functions.
As discussed above, each of the general facsimile, PP-facsimile and PC-facsimile has its own advantages and disadvantages. It is, however, necessary to develop a device that has the functions of these facsimile machines, but is economical and convenient to the user when it is incorporated into a laser printer. In recent years, many efforts have been made to facilitate and maintain high resolution facsimile communication with a host computer or between facsimile machines. One example is shown in U.S. Pat. No. 4,964,154 for Communication Adapter Device For Use with A Facsimile Device Combined With A Computer issued to Shimotono, where a discrete communication adapter is designed to connect between a computer and a host facsimile machine for enabling the computer to freely make mutual correspondence of the image formation between the computer and remote facsimile machines. Various embodiments of this communication adapter are also illustrated in U.S. Pat. No. 4,991,200 for Interface Device For The Intercommunication Of A Computer And A Facsimile Machine issued to Lin, U.S. Pat. No. 5,041,918 for Facsimile Adapter Unit issued to Ishida et al., U.S. Pat. No. 5,280,585 for Device Sharing System Using PCL Macros issued to Kochis et al. These discrete communication adapters connected between the facsimile machine and the computer are, however, costly external devices.
One way to avoid using these external communication adapters is shown in U.S. Pat. No. 5,303,067 for Computer Connection Circuit In Facsimile issued to Kang et al. In Kang et al. '067, a computer connection circuit is built-in a host facsimile machine so as to enable printing of either image signals from a host computer or facsimile information from a remote facsimile machine. In Kang et al. '067, however, image scanner and high resolution printer are still required if high quality image is produced. Another possible solution is illustrated in U.S. Pat. No. 5,091,790 for Multipurpose Computer Accessory For Facilitating Facsimile Communication issued to Silverberg, and U.S. Pat. No. 5,235,674 for Method And Device For Adapting A Printer Into An Autonomous Facsimile Apparatus issued to Cohen-Skalli et al. In both Silverberg '790 and Cohen-Skalli et al. '674, a computer accessory is incorporated in a printer to facilitate facsimile communication from a host computer. In a yet another solution is shown in U.S. Pat. No. 5,072,303 for Combined Printer And Facsimile Apparatus Which Scans Using Different Scan Rates And Dot Sizes issued to Silverberg, a laser printer is modified to perform both the computer printing function and the facsimile image printing function. In these schemes however, although the printer is capable of printing both image signals from a host computer and facsimile messages from a remote facsimile machine, the printer does not have the capability to transmit facsimile messages received from either a remote facsimile machine or a remote computer to a host computer via a public subscriber telephone network for a visual display on a computer screen in accordance with the user's selection. Moreover, the printer also lacks the capability to transmit image signals received from a host computer directly to either a remote facsimile machine for a facsimile print out or a remote computer for a direct or subsequent visual display on a remote screen. Further, these communication adapters are rather complex and costly.