On Sun, 3 Dec 2000 22:31:21 -0800, Galen C Walters wrote:
>I am seeing a continuous -5volts output on pin 3. The 2N2222A certainly
>doesn't like that.
>I thought RS232 ports were standard. What gives??
_____________________________________________________________
They are standard, but they do allow a range of voltages representing
binary 0 or 1. -5 volts is in the range for a 0.
To keep from harming a transistor like your 2N2222A, it is common
practice to place a current limiting resistor in the lead to its base,
usually between 2k and 10k. The base-emitter junction of any bipolar
transistor will act like a zener diode, and as long as the current is
limited, no harm, no foul.
73, Bill W7TI
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