RS232 to 4 RS232 & 4 RS422/RS485 Convertor Distributor
The Milestone LD-1044UD converts a single RS232 input into four RS422/RS485 outputs and four RS232 outputs simultaneously, enabling high-speed serial data distribution over long distances under high-noise industrial conditions, with full opto-isolation and transient protection on every RS485 output.
- Single RS232 input distributed to 4 RS485 outputs and 4 RS232 outputs simultaneously
- RS485 outputs opto-isolated with 2500 V peak transient protection per signal
- Transmission distance up to 1.2 km at 19,200 bps on RS485 outputs
- Mains-powered unit with built-in 230V, 50 Hz power supply, max 50 VA
- Front panel Power and TD LED indicators for real-time status monitoring
Max Resolution
1080p Full HD
Audio Input
Stereo Analogue
Output
Single HDMI
- In-house manufactured
- 24hr response
- 2,000+ clients served
Product Overview
What the LD-1044UD delivers
The Milestone LD-1044UD is a RS232 to RS422/RS485/RS232 convertor-splitter designed for high-speed data transmission between computer systems and peripheral equipment over long distances under high-noise conditions. It accepts a single RS232 input and simultaneously distributes that signal to four RS422/RS485 outputs and four RS232 outputs, making it the right choice for any application requiring one-to-many serial data distribution from a central computer.
All four RS485 outputs are individually opto-isolated, and each signal is protected by a spike suppressor rated at 2500 V peak transient. This level of hardware-level protection makes the LD-1044UD suitable for use in electrically noisy industrial environments such as factory floors, programmable logic controller (PLC) networks, and power distribution installations, where transient spikes can damage or disrupt standard serial interfaces.
For RS485 outputs, the unit supports cable runs of up to 1.2 kilometres at 19,200 bps using twisted pair shielded cable rated at 90 ohms per kilometre. The RS232 input connector is a D9 Female, carrying TxD, RxD, and GND signals on pins 2, 3, and 5 respectively. Each RS422/RS485 output uses a D9 Male connector carrying the differential +Tx/Rx-B and -Tx/Rx-A signals, while each RS232 output uses a D9 Male connector with Rx, Tx, and GND signals.
The unit is mains-powered with a built-in 230V, 50 Hz power supply rated at a maximum of 50 VA, eliminating the need for a separate external adapter. Front panel LED indicators display Power and TD (Tx Data) status, allowing operators to visually confirm that the unit is active and data is being transmitted across the RS485 and RS232 outputs
Input
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Key Features
One RS232 source, eight simultaneous serial outputs
Purpose-built for industrial serial data distribution, with opto-isolated RS485 outputs, 2500 V transient protection, long-distance transmission capability, and built-in mains power.
1 to 8 Serial Output Distribution
A single RS232 input is simultaneously distributed to four RS422/RS485 outputs and four RS232 outputs, enabling one computer or controller to communicate with up to eight peripheral devices across two interface standards without any additional hardware.
- 4 x RS422/RS485 outputs on D9 Male connectors
- 4 x RS232 outputs on D9 Male connectors
- Single RS232 input on D9 Female connector
Opto-Isolation on All RS485 Outputs
Every RS485 output is individually opto-isolated, electrically separating each output circuit from the input and from each other. This prevents ground loop interference and protects both the host computer and connected peripherals in electrically noisy industrial environments.
- Each RS485 output individually opto-isolated
- Prevents ground loop interference between devices
- Protects host computer from field-side faults
2500 V Peak Transient Protection
Each RS485 output signal is individually protected by a spike suppressor rated at 2500 V peak. This level of transient protection guards the unit and connected equipment against voltage spikes common on long industrial cable runs, ensuring reliable operation in high-noise environments.
- 2500 V peak spike suppressor per RS485 output signal
- Suitable for high-noise factory and industrial installations
- Protects connected peripherals from field-side transients
Long-Distance RS485 Transmission up to 1.2 km
The RS485 outputs support data transmission at up to 19,200 bps over cable runs as long as 1.2 kilometres using twisted pair shielded cable rated at 90 ohms per kilometre. This makes the LD-1044UD well suited for plant-wide or building-level serial communication networks where peripheral devices are located far from the host computer.
- Up to 1.2 km cable run at 19,200 bps
- Requires twisted pair shielded cable, 90 ohms per km
- Suitable for plant-wide and multi-zone serial networks
Built-In Mains Power Supply
The LD-1044UD includes a built-in 230V, 50 Hz power supply rated at a maximum of 50 VA. No external adapter or separate power unit is required, simplifying panel or rack installation in industrial control cabinets and server rooms where mains power is directly available.
- 230V, 50 Hz mains input, built-in supply
- Maximum 50 VA power consumption
- No external adapter required
Front Panel LED Status Indication
Two front panel LED indicators provide immediate operational status at a glance. The Power LED confirms that the unit is energised and running. The TD LED confirms that Tx Data activity is present on the RS485 and RS232 outputs, allowing operators to verify live data transmission without external test equipment.
- Power LED confirms unit is energised
- TD LED confirms active Tx Data on outputs
- Front-mounted for easy panel monitoring
Installation
Step-by-step connection procedure
Follow the sequence below to correctly wire the LD-1044UD RS232 input, RS485 outputs, and RS232 outputs. Verify all pin assignments before applying power.
01
Connect the Computer RS232 Port to the Input
Wire the RS232 input cable from the host computer to the D9 Female connector on the unit. For a standard PC COM port (D9 Female), connect: Pin 3 (Tx) on the computer to Pin 2 (Rx) on the unit, Pin 2 (Rx) on the computer to Pin 3 (Tx) on the unit, and Pin 5 (GND) to Pin 5 (Signal Ground). For D25 Female COM ports, use the pin mapping provided in Table IV of the manual. Verify pin assignments for any non-standard computer port before making the cable.
02
Connect RS422/RS485 Output Cables to Peripherals
Connect the RS422/RS485 output devices to the four D9 Male output connectors. Each connector carries +Tx/Rx-B on Pin 5, -Tx/Rx-A on Pin 6, and GND on Pin 7. At the instrument end, connect +Tx (Pin 5) to +Rx on the instrument, and -Tx (Pin 6) to -Rx. Use twisted pair shielded cable rated at 90 ohms per kilometre. Do not route the cable parallel to power line cables, and run the cable through conduit pipe for physical protection on long runs.
03
Connect RS232 Output Cables to Short-Distance Peripherals
Connect peripherals requiring RS232 interface to any of the four RS232 output D9 Male connectors. Each connector carries Rx on Pin 2, Tx on Pin 3, and GND on Pin 5. Wire the Tx pin on the unit to the Rx pin on the connected peripheral, and the Rx pin on the unit to the Tx pin on the peripheral. RS232 outputs are suited for shorter-distance connections within the same cabinet or room.
04
Apply Mains Power and Verify LED Status
Connect the unit to a 230V, 50 Hz mains supply. The built-in power supply will energise the unit automatically. Verify that the Power LED on the front panel illuminates to confirm the unit is operating. When data transmission is active, the TD LED will also illuminate, confirming that Tx Data is present on both the RS485 and RS232 outputs. If the TD LED does not illuminate during expected data transfer, check all input wiring and pin assignments at the RS232 input connector.
Where the LD-1044UD performs
Designed for industrial and commercial environments where a single computer must communicate with multiple serial devices simultaneously, across both short and long-distance cable runs.
Factory Automation Networks
Connect a single supervisory computer to multiple automation devices on the factory floor over RS485. The opto-isolation and 2500 V transient protection guard against the voltage spikes and ground loops common in industrial manufacturing environments.
Programmable Logic Controller Systems
Distribute RS232 data from a master PLC controller to multiple slave PLCs or I/O modules distributed across a plant via RS485 long-distance outputs, while also feeding RS232 outputs to local monitoring or logging equipment.
Attendance Recording Systems
Interface a central attendance management computer with multiple attendance terminals located at different entry and exit points within a facility. The RS485 outputs support the long cable runs required in large premises, while the RS232 outputs connect to local printers or display units.
Barcode Reader Networks
Connect a host inventory or warehouse management computer to multiple barcode scanners or readers via RS232 and RS485 outputs. The LD-1044UD allows simultaneous data collection from multiple scan points without requiring multiple serial ports on the host computer.
Remote Data Transmission and EPABX Systems
Transmit serial data from a central EPABX or communications controller to remote terminals and data collection units at distances up to 1.2 km. The RS485 interface handles long cable runs in multi-floor buildings or campus-wide installations without signal degradation.
Multi-Terminal Data Acquisition
Use the LD-1044UD in data acquisition setups where a single host PC must simultaneously poll or receive data from multiple remote sensors, instruments, or data loggers connected over RS485, while also feeding local display terminals via RS232 outputs.
Full specification sheet
- Input
- RS422/RS485 Outputs
- RS232 Outputs
- Indicators and Power
Max Power Consumption
FAQs about the LD-1044UD
What does the LD-1044UD do?
The LD-1044UD is a RS232 to RS422/RS485/RS232 convertor-splitter. It accepts a single RS232 input from a computer or controller and simultaneously distributes the signal to four RS422/RS485 outputs and four RS232 outputs. This allows one host computer to communicate with up to eight serial peripheral devices at the same time without requiring multiple serial ports or additional interface hardware.
What is the maximum cable distance for the RS485 outputs?
The RS485 outputs support transmission at up to 19,200 bps over a maximum cable distance of 1.2 kilometres. This distance is achieved using twisted pair shielded cable with a resistance rating of 90 ohms per kilometre. The cable must not be routed parallel to power line cables to avoid interference, and should be installed through conduit pipe for physical protection on long cable runs.
Are the RS485 outputs opto-isolated?
Yes. Each of the four RS485 outputs is individually opto-isolated. In addition to opto-isolation, each output signal is protected by a spike suppressor rated at 2500 V peak transient. This combination of opto-isolation and transient protection makes the RS485 outputs suitable for use in industrial environments where high-voltage spikes, ground potential differences, and electromagnetic interference are present on field cabling.
What type of cable should be used for the RS485 output connections?
Twisted pair shielded cable rated at 90 ohms per kilometre must be used for the RS422/RS485 output connections. One twisted pair should be used for each differential signal pair, meaning one pair carries the +Tx/Rx-B and -Tx/Rx-A signals together. The cable should not be run parallel to power cables, and should be routed through conduit pipe for protection. The cable resistance must not exceed 90 ohms per 1000 metres to achieve the rated 1.2 km transmission distance.
What is the correct pin wiring for the RS232 input connector?
The RS232 input is a D9 Female connector. For a standard PC COM port with a D9 Female connector, the wiring is: computer Pin 3 (Tx) connects to unit Pin 2 (Rx), computer Pin 2 (Rx) connects to unit Pin 3 (Tx), and computer Pin 5 (GND) connects to unit Pin 5 (Signal Ground). For a D25 Female COM port, the mapping uses D25 Pin 2 to unit Pin 3, D25 Pin 3 to unit Pin 2, and D25 Pin 7 to unit Pin 5. Pin assignments should always be verified for any non-standard computer or terminal before making the cable.
Can the RS232 outputs and RS485 outputs be used at the same time?
Yes. The LD-1044UD is designed to drive all four RS422/RS485 outputs and all four RS232 outputs simultaneously from the single RS232 input. There is no switching or selection required between output types. All eight outputs carry the same data from the RS232 input at the same time, allowing a single host computer to broadcast serial data to multiple devices across both interface standards concurrently.
What power supply does the LD-1044UD require?
The LD-1044UD includes a built-in mains power supply accepting 230V, 50 Hz input with a maximum power consumption of 50 VA. No external adapter or separate power unit is required. The unit connects directly to a standard mains supply. This built-in supply makes the LD-1044UD straightforward to install in industrial control panels and server rooms where mains power is readily available at the mounting location.
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