The RS232 to RS422 Converter is an industrial communication adapter designed to convert standard single-ended, short-distance RS-232 serial signals into balanced differential, full-duplex RS-422 signals. By transitioning from ground-referenced RS-232 voltage levels to noise-immune differential transmission lines, it extends serial communication ranges from 15 meters (50 feet) up to 1,200 meters (4,000 feet) while supporting transmission speeds up to 115.2 kbps. Equipped with an efficient internal charge-pump/stealing power circuit, it typically draws operational power directly from the host RS-232 handshake lines (TXD, RTS, DTR) without requiring an external DC power supply, and features integrated TVS surge suppression on all differential lines to protect industrial equipment against ground loops, EMI, and static discharge.

Specifications

• Product Type: Asynchronous, Full-Duplex RS-232 to RS-422 Industrial Protocol Converter
• Serial Compatibility: Fully compliant with EIA/TIA RS-232C and RS-422 standards
• RS-232 Interface Connector: DB9 Female (Directly mates with standard PC COM ports)
• RS-422 Interface Connector: DB9 Male connector bundled with a 5-Pin / 6-Pin Pluggable Screw Terminal Block
• Transmission Mode: Asynchronous, Full-Duplex, Point-to-Multipoint, 4-Wire Differential (T+, T-, R+, R-, GND)
• Baud Rate / Data Transmission Speed: 300 bps to 115.2 kbps (Auto-negotiated baud rate sensing)
• Maximum Transmission Distance:
  • RS-232 Side: Up to 15 Meters (50 Feet) at 9600 bps
  • RS-422 Side: Up to 1,200 Meters (4,000 Feet) at 9600 bps; ~100m at 115.2 kbps
• Power Supply Source: Port-powered via RS-232 lines (TXD, RTS, DTR); optional external DC 5V–12V auxiliary input header
• Power Consumption: ≤ 10 mA to 15 mA (Ultra-low static power draw)
• Multi-Drop Capacity: Supports up to 32 RS-422 slave transceiver nodes on a single multi-drop bus
• Surge & ESD Protection: Integrated 600W TVS (Transient Voltage Suppressor) per line and ±15kV Human Body Model (HBM) ESD protection
• Transmission Media: High-grade Shielded Twisted Pair (STP / UTP, 24 AWG to 22 AWG) or dedicated industrial communication cable
• Operating Temperature Range: -20°C to +70°C (-4°F to 158°F)
• Relative Humidity: 5% to 95% (Non-condensing)
• Enclosure Dimensions: Approx. 63 mm × 33 mm × 17 mm (Excluding terminal block extension)
• Weight: Approx. 35 g to 50 g

Pinout & Terminal Definition

• RS-232 Side (DB9 Female Connector):
  • Pin 2: RXD – Receive Data
  • Pin 3: TXD – Transmit Data
  • Pin 5: GND – Signal Ground (0 V)
  • Pins 4 (DTR), 7 (RTS), 8 (CTS): Handshake lines (internally utilized for port-power harvesting)
• RS-422 Side (5-Pin Screw Terminal Block / DB9 Male):
  • Terminal 1 (T+ / TXA / 422-Y): Transmit Data Non-Inverting (+)
  • Terminal 2 (T- / TXB / 422-Z): Transmit Data Inverting (-)
  • Terminal 3 (R+ / RXA / 422-A): Receive Data Non-Inverting (+)
  • Terminal 4 (R- / RXB / 422-B): Receive Data Inverting (-)
  • Terminal 5 (GND / PE): Signal Ground / Shield Earth Connection

Features

• True Full-Duplex 4-Wire Communication: Separate differential transmit (T+/T-) and receive (R+/R-) channels allow simultaneous two-way data transmission without software turnaround delays.
• Port-Powered Operation (No External PSU Required): Patented onboard charge pump harvests necessary operating energy directly from RS-232 data and handshake pins, simplifying wiring in field deployments.
• Long-Distance Extension (Up to 1.2 km): Converts noise-sensitive, single-ended signals to balanced differential voltage signals, overcoming industrial EMI, RFI, and long-run line attenuation.
• Multi-Drop Networking: Capable of driving up to 32 RS-422 slave devices in a distributed master-slave telemetry or factory monitoring network.
• Built-In Transient Voltage Suppression: 600W TVS diodes clamp high-voltage lightning surges and electrostatic discharges, preventing motherboard serial port damage.

Common Applications

• PLC & CNC Machine Programming: Bridging legacy PC serial ports with industrial Programmable Logic Controllers, HMIs, and CNC machine controllers.
• PTZ Security Camera Control: Driving long-run Pelco-D / Pelco-P RS-422 telemetry control lines for pan-tilt-zoom surveillance cameras.
• Factory Automation & SCADA: Interfacing building automation sensors, barcode scanners, digital scale indicators, and flow meters to centralized SCADA servers.
• Access Control & Time Attendance: Connecting distributed RFID card readers, biometric turnstiles, and security gates over long physical distances.
• Broadcast & Pro-Audio Control: Controlling professional video switchers, broadcast routers, and robotic camera heads via Sony 9-pin RS-422 protocol.

Usage Tips

• Wiring Polarity & Cross-Over (CRITICAL):
  • In point-to-point RS-422 connections, Transmitter (T+/T-) must connect to the remote Receiver (R+/R-), and Receiver (R+/R-) must connect to the remote Transmitter (T+/T-).
  • Always wire matching polarities together: T+ connects to R+, and $T- connects to R-. Crossing polarities (T+ to R-) will invert logic levels and cause framing errors or communication failure.
• 120Ω Termination Resistors: On long cable runs (>100 meters) or high baud rates (>19.2 kbps), place a 120Ω (1/4W) terminating resistor across the R+ and R- differential pair at the far end of the transmission line to prevent signal reflection.
• Cable Selection: Always use Shielded Twisted Pair (STP) cabling. Pair T+ with T- in one twisted pair, and R+ with R- in a separate twisted pair. Connect the outer foil/braid shield to the GND terminal at one end only to prevent ground loops.
• Auxiliary Power Use: If using passive USB-to-RS232 adapters or low-power embedded microcontrollers whose handshake lines do not provide sufficient current for port powering, connect an external 5V DC regulated power supply to the auxiliary power terminals on the converter.
• Grounding: While RS-422 uses differential signaling, connect the common GND between both communicating devices to keep common-mode voltage within the standard safe window of -7V to +12V.