AUTOMATIC SYNCHRONOUS OR ASYNCHRONOUS COMMUNICATIONS SWITCHING DEVICE

摘要

PURPOSE: To unnecessitate a line exclusively for discriminating a synchronous type or an asynchronous type by switching communication from a transmission side to synchronous or asynchronous corresponding to the detection voltage of a voltage level detection means. ;CONSTITUTION: When high level signals are supplied to a transmission signal input terminal 3, a transistor 4 for transmission is turned to a nonconductive condition. At the time, a reception side terminating resistor R₂ as a pull-down resistor is present on the side of a computer 2 and a voltage between ground on the side of the computer 2 and a power supply voltage VCC on the side of a display monitor 1 is voltage-divided by the reception side terminating resistor R₂ and a resistor R₁ as a pull-up resistor on the side of the display monitor 1 through a transmission line 9. As a result, the transmission line 9 is turned to a low level and the side of the display monitor 1 is switched to synchronous type communication. Also, when the reception side terminating resistor R₂ on the side of the computer 2 is not present, the transmission line 9 is turned to a high level by a power supply voltage VCC resistor R₁ on the side of the display monitor 1 and the side of the display monitor 1 is switched to asynchronous type communication.;COPYRIGHT: (C)1995,JPO