LM393 comparator witch Isteresis....problem

[buddace]

Hello, this is schematic of loconet tranceiver (one wire serial line) (I add 1k pullup resistor)
**broken link removed**
I have problem whit lm393...it don't work correctly...some times. With high input out is Low....

 

[helios31]

LM393 has an open collector output, not visible on your schematic. Unless present outside, this is not correct.

 

[buddace]

There is 1k pullup between pin1 and vcc (not in schematic)