Schematic symbol for zero crossing detector

[Ludis Langens]

I wish to create a schematic symbol for a chip which contains a zero
crossing detector.  Instead of just a black box, I'd like to make the
functionality obvious with a mini-schematic of a zero crossing detector.

The detector functions as follows:  If the input voltage is much below
zero, or much above zero, the digital output is "low".  If the input
voltage is close to zero, the output is "high".  This is different than
a simple comparator checking against zero volts.

Is there a standard symbol for this?  It could be drawn/built with two
comparators but the input would need lots of resistor biasing because
there is no negative power supply.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/