A Four-Channel RS-422 Differential Line Receiver and Transmitter Module
This Quadruple Differential Line Driver module provides four independent differential output channels for driving balanced transmission lines in industrial and embedded applications. Built around the Texas Instruments AM26LS31 IC in a DIP-16 package, the module meets TIA/EIA-422-B and ITU standards. It delivers high-current 3-state outputs capable of driving twisted-pair or parallel-wire transmission paths. In my next project, I will show you how to build the complementary four-channel RS-422 differential line receiver.
An onboard LM7805C regulator accepts 7–18V DC input and supplies a stable 5V rail to the driver IC. The assembled module is shown in Figure 1.
All four driver channels share a common enable circuit with both active-high (G) and active-low (!G) enable inputs, brought out to solder jumpers on the back of the PCB. This flexibility allows the module interface to communicate directly with microcontrollers or PLCs regardless of the enable polarity.
Screw terminals (5.08 mm pitch) connect the four differential output pairs to a transmission cable, while an 8-pin header provides the digital data inputs at 2.54 mm pitch for easy breadboard or jumper-wire connection.
When power is removed, the 3-state output stage automatically places all outputs in a high-impedance condition, preventing bus loading in multi-drop configurations. The module targets applications including industrial encoder interfaces, fieldbus sensor transmitters, Modbus temperature controllers, and motor control systems where data integrity over cable runs is critical.
Specs and Features
- Supply voltage: 7–18 VDC
- 4-channel differential output (TIA/EIA-422-B / ITU compliant)
- Key IC: AM26LS31 (DIP-16, Bi-CMOS)
- 3-state outputs with high-impedance power-off condition
- Active-high (G) and active-low (!G) enable inputs via solder jumpers
- Onboard 5 V regulator: LM7805C (TO-220), with reverse-polarity diode protection
- Output screw terminals: 5.08 mm pitch (CN1, CN4, CN5, CN7)
- Digital input header: 8-pin, 2.54 mm pitch (CN3)
- Power LED indicator
- PCB dimensions: 46.36 × 30.48 mm
- Four 3 mm mounting holes
This design is for a quadruple differential line receiver designed for balanced or unbalanced digital data transmission over RS-422 and RS-485 links. It accepts four independent differential input pairs and converts them to single-ended digital outputs suitable for direct connection to a microcontroller or bus-organized system. It also complements our previous project, a four-channel RS-422 differential line driver.
The fully assembled board is shown in Figure 1. All four receivers share a common enable function with both active-high and active-low control inputs, and the 3-state outputs allow safe multi-device bus sharing.
Specs and Features
- Power input: 7 to 18 VDC
- On-board 5 V regulation via LM7805
- ±7 V common-mode range with ±200 mV sensitivity
- Input hysteresis: 60 mV typical
- 3-state outputs — bus-compatible
- Fail-safe: open inputs default to logic high
- Common enable with active-high and active-low inputs (solder-jumper selectable)
- Four 120 Ω on-board termination resistors
- On-board power LED
- Screw terminals for twisted-pair input cables (5.08 mm pitch)
- 8-pin output header for microcontroller interfacing (2.54 mm pitch)
- PCB dimensions: 55.25 mm × 37.47 mm
- Four 3 mm mounting holes
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This Quadruple Differential Line Driver module provides four independent differential output channels for driving balanced transmission lines in industrial and embedded applications. Built around the Texas Instruments AM26LS31 IC in a DIP-16 package, the module meets TIA/EIA-422-B and ITU standards. It delivers high-current 3-state outputs capable of driving twisted-pair or parallel-wire transmission paths. In my next project, I will show you how to build the complementary four-channel RS-422 differential line receiver.
An onboard LM7805C regulator accepts 7–18V DC input and supplies a stable 5V rail to the driver IC. The assembled module is shown in Figure 1.
All four driver channels share a common enable circuit with both active-high (G) and active-low (!G) enable inputs, brought out to solder jumpers on the back of the PCB. This flexibility allows the module interface to communicate directly with microcontrollers or PLCs regardless of the enable polarity.
Screw terminals (5.08 mm pitch) connect the four differential output pairs to a transmission cable, while an 8-pin header provides the digital data inputs at 2.54 mm pitch for easy breadboard or jumper-wire connection.
When power is removed, the 3-state output stage automatically places all outputs in a high-impedance condition, preventing bus loading in multi-drop configurations. The module targets applications including industrial encoder interfaces, fieldbus sensor transmitters, Modbus temperature controllers, and motor control systems where data integrity over cable runs is critical.
Specs and Features
- Supply voltage: 7–18 VDC
- 4-channel differential output (TIA/EIA-422-B / ITU compliant)
- Key IC: AM26LS31 (DIP-16, Bi-CMOS)
- 3-state outputs with high-impedance power-off condition
- Active-high (G) and active-low (!G) enable inputs via solder jumpers
- Onboard 5 V regulator: LM7805C (TO-220), with reverse-polarity diode protection
- Output screw terminals: 5.08 mm pitch (CN1, CN4, CN5, CN7)
- Digital input header: 8-pin, 2.54 mm pitch (CN3)
- Power LED indicator
- PCB dimensions: 46.36 × 30.48 mm
- Four 3 mm mounting holes
This design is for a quadruple differential line receiver designed for balanced or unbalanced digital data transmission over RS-422 and RS-485 links. It accepts four independent differential input pairs and converts them to single-ended digital outputs suitable for direct connection to a microcontroller or bus-organized system. It also complements our previous project, a four-channel RS-422 differential line driver.
The fully assembled board is shown in Figure 1. All four receivers share a common enable function with both active-high and active-low control inputs, and the 3-state outputs allow safe multi-device bus sharing.
Specs and Features
- Power input: 7 to 18 VDC
- On-board 5 V regulation via LM7805
- ±7 V common-mode range with ±200 mV sensitivity
- Input hysteresis: 60 mV typical
- 3-state outputs — bus-compatible
- Fail-safe: open inputs default to logic high
- Common enable with active-high and active-low inputs (solder-jumper selectable)
- Four 120 Ω on-board termination resistors
- On-board power LED
- Screw terminals for twisted-pair input cables (5.08 mm pitch)
- 8-pin output header for microcontroller interfacing (2.54 mm pitch)
- PCB dimensions: 55.25 mm × 37.47 mm
- Four 3 mm mounting holes
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