Milestone Electronics
RS232 Isolator
The LD-14I provides optical isolation between two RS232 communicating devices, protecting expensive system interfaces from transient damage. Designed for industrial environments where electrical noise and voltage spikes are a concern.
- 2500V peak optical isolation between input and output port circuit
- 2500V peak transient protection for connected equipment
- Supports RS232 signals: TxD, RxD, DTR, DSR and Signal GND
- D9 Female connector on input port and D9 Male connector on output port
- Built-in 230V mains power supply, max 20 VA
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-14I delivers
The Milestone RS232 Isolator LD-14I is designed to protect expensive system interfaces by providing optical isolation between two communicating RS232 devices. By electrically decoupling the input and output port circuits, the unit prevents ground loops, transient voltages, and electrical noise from passing between connected equipment.
The isolator supports the RS232 signal set of TxD, RxD, DTR, DSR, and Signal GND. The input port uses a D9 Female connector and the output port uses a D9 Male connector, allowing straightforward insertion into existing RS232 cable runs without additional adapters.
With 2500V peak optical isolation and 2500V peak transient protection, the LD-14I is suited for industrial environments where voltage spikes and electrical interference are a concern. Front panel LED indicators for TD, RD, Power, DTR, and DSR provide real-time signal status visibility during operation.
The unit is powered directly from 230V mains at 50 Hz through a built-in power supply rated at a maximum of 20 VA, eliminating the need for a separate external power adapter. Its compact 107mm x 105mm x 55mm enclosure allows installation in space-constrained environments.
Optical Isolation
Need a quote?
Our team responds within 24 hours with a tailored quote for your project or bulk order.
Key Features
Optical isolation and transient protection for RS232 interfaces
The LD-14I combines high-voltage optical isolation, transient suppression, and real-time signal indication in a compact mains-powered unit for RS232 interface protection.
2500V Peak Optical Isolation
The LD-14I provides 2500V peak optical isolation between the input and output port circuits. This electrically decouples the two communicating RS232 devices, preventing ground loop currents and high-voltage transients from crossing between them and damaging connected equipment.
- Optical barrier rated at 2500V peak between input and output
- Prevents ground loop interference between devices
- Protects sensitive RS232 interface circuitry from electrical damage
2500V Peak Transient Protection
In addition to optical isolation, the unit incorporates 2500V peak transient protection. This guards connected devices against voltage spikes that can originate from industrial machinery, power switching events, or other noise sources present in factory and automation environments.
- Transient suppression rated at 2500V peak
- Protects against voltage spikes from industrial equipment and power events
- Suitable for electrically noisy factory and automation environments
Full RS232 Signal Support
The isolator supports the complete set of RS232 signals required for standard device communication: TxD, RxD, DTR, DSR, and Signal GND. RTS, CTS, and CD lines are also present on both connectors, ensuring compatibility with a wide range of RS232 peripherals and host systems.
- TxD, RxD, DTR, DSR, and Signal GND on both input and output ports
- RTS, CTS, and CD lines available on D9 connectors
- Compatible with standard RS232 devices and serial peripherals
Front Panel Signal Indicators
The front panel carries five LED indicators: TD, RD, Power, DTR, and DSR. These provide at-a-glance confirmation of signal activity and power status, making it straightforward to verify that the unit is operational and that data is flowing correctly between connected devices.
- Dedicated LEDs for TD, RD, Power, DTR, and DSR
- Instant visual confirmation of signal activity and device power
- Simplifies troubleshooting and installation verification
Built-in 230V Mains Power Supply
The LD-14I includes an integrated power supply accepting 230V AC at 50 Hz, rated at a maximum of 20 VA. This eliminates the need for a separate external adapter, simplifying installation and reducing cabling in equipment racks and control panels.
- Accepts 230V AC, 50 Hz mains input directly
- Maximum power consumption of 20 VA
- No external power adapter required
Compact Enclosure
With overall dimensions of 107mm x 105mm x 55mm, the LD-14I occupies minimal space in control panels, equipment cabinets, and industrial enclosures. The compact form factor makes it practical to install close to the devices being protected without requiring dedicated rack space.
- Dimensions: 107mm x 105mm x 55mm
- Suitable for control panels, equipment cabinets, and industrial enclosures
- No dedicated rack unit required
Installation
Inline RS232 connection between two devices
The LD-14I installs directly in the RS232 cable path between the host system and the peripheral device. The D9 Female input port connects to the host or controller side, and the D9 Male output port connects to the target RS232 device.
01
Connect the Input Port
Connect the RS232 cable from the host system, controller, or PC to the D9 Female connector on the input port of the LD-14I. The input port carries TxD (Pin 3), RxD (Pin 2), Signal GND (Pin 5), DTR (Pin 6), DSR (Pin 4), and RTS, CTS, CD on Pins 7, 8, and 1 respectively. Ensure the cable pinout matches the device being connected.
02
Connect the Output Port
Connect the RS232 cable from the output port of the LD-14I to the target peripheral device. The output port uses a D9 Male connector carrying TxD (Pin 3), RxD (Pin 2), Signal GND (Pin 5), DSR (Pin 6), DTR (Pin 4), and RTS, CTS, CD on Pins 7, 8, and 1. Note that signal directions are inverted relative to the input port to maintain correct data flow.
Where the LD-14I is used
Designed for industrial and commercial environments where RS232 devices must be isolated from each other to prevent damage caused by electrical noise, ground differences, or transient voltage events.
Factory Automation
Isolates RS232 communication lines between industrial controllers, sensors, and host systems in manufacturing environments where electrical noise from motors and heavy machinery can damage unprotected serial interfaces.
Programmable Logic Controllers
Provides a protected RS232 link between PLCs and connected peripherals or host computers. Optical isolation ensures that voltage differences between the PLC ground and the host system ground do not cause current flow or equipment failure.
Barcode Readers
Protects barcode reader RS232 interfaces in retail, logistics, and warehouse environments where scanners are frequently connected and disconnected from host systems, creating transient events that can degrade or damage serial ports over time.
EPABX and Telephony Systems
Isolates the RS232 management or programming port of EPABX telephone exchange systems from connected PCs or laptops, preventing ground-related faults from entering the exchange hardware during maintenance or configuration sessions.
Remote Data Transmission
Used in remote data acquisition and transmission setups where RS232 cabling runs across long distances or between buildings with different electrical ground potentials, where isolation is necessary to maintain reliable communication and prevent equipment damage.
Attendance Recording Systems
Protects the RS232 interface between attendance recording terminals and the host management computer. Isolation prevents damage caused by power surges or ground potential differences in multi-floor or multi-building installations where terminals are connected to separate power circuits.
Full specification sheet
- Signal Interface
- Input Port Pin Assignment (D9 Female)
- Output Port Pin Assignment (D9 Male)
- Protection
- Power Supply
- Indicators and Physical
FAQs about the RS232 Isolator LD-14I
What is the purpose of the LD-14I RS232 Isolator?
The LD-14I is designed to protect expensive system interfaces by providing optical isolation between two communicating RS232 devices. It prevents ground loop currents, voltage transients, and electrical noise from passing between the connected host system and its RS232 peripheral, thereby protecting both devices from damage. It is particularly suited to industrial and commercial environments where electrical interference is common.
What level of isolation does the LD-14I provide?
The LD-14I provides 2500V peak optical isolation between the input and output port circuits. It also incorporates 2500V peak transient protection, which guards connected equipment against voltage spikes that may occur due to switching events, industrial machinery, or power disturbances on the connected lines.
What RS232 signals are supported by the LD-14I?
The LD-14I supports TxD, RxD, DTR, DSR, and Signal GND on both the input and output ports. RTS, CTS, and CD lines are also present on both the D9 Female input connector and the D9 Male output connector. This covers the standard RS232 signal set required for most serial device communication applications.
What type of connectors does the LD-14I use?
The input port of the LD-14I uses a D9 Female connector, which connects to the RS232 cable coming from the host system or controller. The output port uses a D9 Male connector, which connects to the target RS232 peripheral device. This arrangement allows the isolator to be inserted directly into the existing RS232 cable path without requiring additional adapters in most standard configurations.
What are the typical applications for this isolator?
The LD-14I has a built-in power supply that accepts 230V AC mains input at 50 Hz with a maximum power consumption of 20 VA. No external power adapter is required. This makes installation straightforward, as the unit can be powered directly from a standard mains socket near the installation point.
How is the LD-14I powered?
The ML 104 AV supports composite video signals with a bandwidth of up to 90 MHz (-3dB). The nominal signal level is 1V peak-to-peak, with a compatible input range of 0.4V to 1.4V. The 75-ohm impedance ensures proper signal matching with standard composite video equipment.
How can I verify that the LD-14I is operating correctly after installation?
The front panel of the LD-14I carries five LED indicators: TD, RD, Power, DTR, and DSR. Once the unit is powered on, the Power LED should illuminate to confirm the internal power supply is active. When data is exchanged between the connected devices, the TD and RD indicators will show activity. The DTR and DSR LEDs indicate the state of the handshaking lines, allowing you to confirm that both devices have established their control signal states correctly.
What is the maximum cable distance supported by the LD-14I?
The LD-14I supports a maximum RS232 transmission distance of 15 metres. This is consistent with the RS232 standard specification for reliable serial communication. The isolator should be placed within this distance from the devices on either side of the installation to ensure correct signal integrity across the protected link.
Products you may also need
The LD-15U is a reliable converter that enables communication between RS232 devices and RS422...
The LD-15PN is a panel-mounted converter that enables communication between RS232 devices and RS422...