Use of Universal Input UI1 on a Microzone II as a pulse counter requires an external pull-up resistor.
TAC I/A Series
High speed count input required a 10 K ohm shunt resistor.
When UI1 on the Microzone II is used as a Pulse Counter, an external pull-up resistor must be added between UI1 and the 5.1 VDC output terminal. The resistor shall be a 10 K Ohm, 1/4 Watt or higher, +/- 10% tolerance or better. Universal Inputs UI2 - UI8 do not require the resistor.