Wiegand Interface - Unwanted Capacitance

A third problem with using a single twisted pair for Wiegand data transmission is that the tight twist of the wires produce unwanted capacitance

• The built up charge effectively fills in the hole that would have represented a bit of data, resulting in part of the card read missing, and therefore a failed card read
• This symptom would present itself as an intermittent card read failure, usually in the first card read following some time of inactivity