TRP-C28         4-CH isolated digital input and 4-CH power relay  output RS-485 module             Support ASCII and Modbus RTU protocol



TRP-C28 provides with 4 optical isolated digital input channels and 4 power relays output. All channel features screw terminals for convenient connection of field signals as well as LED’s to indicate channel status.  Input channels are equipped with 3750Vms DC isolation, and surge protection on RS-485 data lines that protect the module and divece against high power voltage input and ground potential differences. For easy user access, TRP-C28 can enter configuration mode and self-test mode with outer dip-switch. TRP-C28 support both ASCII and Modbus protocol, with a full set of command, dual watch-dog, and auto reset function the module can be bi-directionally remote controlled by PC in ASCII or Modbus RTU protocol.


  • Wide input range DC power supply..
  • Support ASCII and Modbus RTU protocol.
  • Supports baud rates from 1.2Kbps to 115.2 Kbps.
  • All 4 channels digital input ca be used as counter.
  • Digital input signal with 3750Vrms isolation protection.
  • Dual watchdog: Module’s firmware, host computer traffic.
  • LED for each channels working status.
  • DIN rail and panel mount support.
  • Configured and self-test by outer dip-switch.
  • Support screw terminal and external DC power adaptor.
  • Fully compatible with SCB-C28.


  • Input channel: 4 digital input channels.
  • Input optical isolation: 3750 Vrms.
  • Input logical level 0 +1/-V (max).
  • Input logical level 1 +/-4.0V ~ +/-30V.
  • Digital output Maximum voltage: +/-30V.
  • Communication interface: RS-485.
  • Communication speed: Baud rate from .2kbps to 115.2Kbps.
  • Input impedance: 3Kohm.
  • Distance: 500M (max).
  • Digital Input can be used as counter channel: 4
  • Counter frequency: 100Hz.
  • Output channel: 4 channel power reply outputs.
  • Relay type: 2 Form A (RL1,RL2) , 2 Form C (RL3,RL4).
  • Contact ratting: 5A /30V DC , 5A /120V AC , 5A /250V AC.
  • Relay surge strength: 4000V.
  • Relay operating time: 3mS.
  • Relay operating life: 2 X 10(7).
  • Dual watchdog: Hardware reset circuit, module and host operating status.
  • Signal LED: Power on, all channels.
  • Power supply: Screw terminal, or external DC adapter.
  • Connection type: Screw terminal, accepts AWG #12~320 wires
  • Power consumption: 2.7W.
  • Operating environment: -10 to 50℃.
  • Storage temperature: -20 to 70℃.
  • Humidity: 10-90% Non-condensing.
  • Dimension: 151mm X 75mm X 26mm .
  • Weight: 400g .


PWR-AD12VAuto (Option)

Switching Adaptor

Input:100~240VAC 50/60Hz 260mA

Output: DC 12V/1A

Certificate: CE, FCC, UL, PSE

US Specification  

We also provide the EU / AUS / British specifications(MOQ:50PCS/2 Weeks)……more

DIN-RAIL-R (Option)

DIN rail mounting adapter