Msg: 5411 *Conference*

09-11-94 21:50:58

From: DREW BLANCHAR

To : COMET _

Subj: REPLY TO MSG #5245 (TAPE)

Sure....I'll tell you why the TAPE control plug doesn't just "ground" your REM
connection......

Tandy, in a very rare insight, realized that it's far safer to make the
controller a "balanced" relay closure.....NO voltage on the controller pins
interact with any part of the computer's circuitry....._T_O_T_A_L_
isolation.....the safest way to hand the inductive kick of cassette motors and
it doesn't care at all about the polarity or voltage (up to the limits of the
relay contacts. 


Now, look at the isolation on the BAR CODE input.  Any time you're running
signals off the CMOS circuit board to peripheral devices (especially on clunky
cables or home brewed devises) you want to design in protection (like filtering
or isolation).