| 摘要 |
An automatic detection and selection circuit (10) resident in a DCE is provided. The circuit (10) is coupled to the DCE in- terface connector and detects receipt by the DCE of V.35 and RS-232 transmit data signals, distinguishes between those signals, and selects circuitry for passing the data therethrough. The circuit compris es a switch (20) coupled to a first TX data terminal (pin 2 or P) of the DCE interface connector, first and second line receiving circuits (30, 50), a microprocessor (75), and relay (82). The first line receiving circuit (30) is coupled to a first pole of the switch (20) and to the second TX data terminal (pin S) of the DCE interface connector and provides indications as to whether or not an input signal is present at at least one of pins P and S. The second line receiving circuit (50) is coupled to the second pole of the swit ch (20) and provides indications as to whether or not a valid RS-232 transmit data signal is detected.
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