On Sun, 13 Feb 2011 16:59 -0800, "Bob Blick" wrote:

> In my limited experience I would say there is hysteresis.=20
>=20
> The logic high voltage does not vary with supply and is based on the
> internal voltage regulator of the servo chip, which is somewhere around
> 3 volts.

Had a Signetics NE544 datasheet on my hard drive. Input impedence 18
kohm. Logic "1" 1.5 volts. Logic "0" 1.4 volts. All ratings typical.

So my memory would have been good enough.

Bob

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