Abstract: Data communications between a FAX modem (36) and a facsimile (38) can be performed without using a telephone line. Electric characteristics of a line (44) are interrupted in view of direct current, and is connected in view of alternating current by a capacitor (C1). When an off-hook detection circuit (62) detects an off-hook state of the FAX modem (36), and the off-hook detection circuit (62) puts the direct current converter 60 in operation, a telephone line emulation voltage is applied to the line (44). A ringback signal is outputted to the line (44) by a ringback signal output circuit (66) as a result of a judgement of the ringback signal output circuit that it is a transmission from the FAX modem when an answering tone is not detected for predetermined duration. Data communication between the FAX modem (36) and the facsimile (38) can then be performed by calling the facsimile machine (38).

Abstract: On receiving a digital signal from a computer (2), a frequency detector (28) determines a transmitting speed for computer (2). When the computer (2) has an operating frequency of 7.9872 of MHz, a speed other than one of the standardized speeds is selected to implement communication between the computer (2) and the frequency detector (28) at a speed of more than 9600 bps. To do this communication, the frequency detector (28) has a table for obtaining the speed other than one of the standardized speeds.

Abstract: Data communication system between computers; communication paths composed of m transmission lines are formed between two computers, and data to be transferred are coded based on a coding table comprised of encoding codes. When transmitting, state of the m transmission lines 74, 76 and 78 is changed. Therefore, timing signal is not required.

Abstract: A method for parallel data transmission in a system having (i) a modem, (ii) one or more modem status terminals which detect modem status information and are connected to the modem, (iii) one or more modem control terminals which transmit modem control signals and are connected to the modem, and (iv) one or more serial signal output terminals which receive line control signals and are connected to the modem. Data signals are output via the one or more modem control terminals. Signal logic levels of these output data signals are controlled in accordance with the modem control signals. Data signals are also output via the one or more serial signal output terminals. The signal logic levels of these later output data signals are controlled in accordance with the line control signals. Data signals are input via one or more modem status terminals. The signal logic levels of the input data signals are perceived in accordance with the modem status information.

Abstract: A data communication system between computers comprises communication paths composed of m transmission lines between the computers. Data and data to be transferred is coded based on a coding table. Each code comprises a series or string of figures. Each figure has a numeric value not over the m-th power of 2. Also, those adjacent figures in each code string have necessarily different values. Coded data is transmitted figure by figure through m transmission lines. Since values of each figure in a code necessarily differ, a timing signal is not required.