... and transducer, current and pulse output, alarm signal and RS-485 communication.3. Special Features- zero pressure losing;- Corrosion ... or 4~20mA;- Frequency Output: 0~5000Hz with photoelectric isolation;- Pulse Output: 0.001~1.000m3/cp, 0 ... Upper Alarm-ALMH, Lower Alarm-ALML with photoelectric isolation;- Communications: RS-232 without galvanic isolation, RS-485 with Galvanic isolation,MODBUS.