Logic Controlled Relay-Dual Alternate Pulse

The RDL ST-LCR3 is a dual alternate-pulse, logic-controlled relay for applications requiring a pulse at both the start and the end of a logic signal. It combines two single-pole relay contacts with two open-collector outputs, providing both relay-contact and electronic pulse interfaces. Its two inputs accept active-high or active-low logic, with a logic-low level referenced to ground and a logic-high range of 3.3 to 24 Vdc.

Ideal Use Cases

The ST-LCR3 is suited to control systems that must respond separately when a logic signal begins and when it ends. Control can originate from a switch, pushbutton, or logic circuit, allowing the module to work with several common control methods. The open-collector outputs can drive indicators or slave LCRs, while the relay contacts provide an additional switching interface.

• Generating a pulse at the start of a logic signal
• Generating a pulse at the end of a logic signal
• Operating from active-high or active-low control inputs
• Driving indicators or slave LCRs through open-collector outputs
• Accepting control from switches, pushbuttons, or logic circuits

Why Choose This Model

The defining advantage of the ST-LCR3 is its combination of start-of-signal and end-of-signal pulse functions. It provides two logic inputs, two open-collector outputs, and two single-pole relay contacts in one model. This makes it useful when a control design needs access to both electronic outputs and physical relay contacts. Its supported logic-high input range of 3.3 to 24 Vdc also accommodates control voltages commonly encountered across different logic systems.

Each open-collector output is rated at 25 mA and is specified as suitable for indicators or slave LCRs. The published maximum switching power for the relay contacts is 60 W, with the supplied rating notation of 220 Vdc, 125 Vac, and 2 A.

Installation and Integration

The ST-LCR3 requires ground-referenced 24 Vdc power at 100 mA, based on an assumed maximum 20 mA load at the SLAVE output. A power supply is not included. The recommended supplies listed for the module are the PS-24AS for the USA and the PS-24AX for international use.

When connecting the two control inputs, logic low is ground and logic high may range from 3.3 to 24 Vdc. The inputs support either active-high or active-low operation. This permits integration with a switch, momentary pushbutton, or logic circuit, provided the connected control source remains within the stated input range. Loads connected to the relay contacts or open-collector outputs should remain within their published ratings.

Performance Highlights

The module operates in ambient temperatures from 0° C to 55° C. Its two open-collector outputs are rated at 25 mA, while its two switching outputs use single-pole relay contacts. Together, these interfaces allow the pulse response to be used for indicator operation, slave LCR control, or switching through the relay contacts.

• Two logic-high or logic-low inputs
• Logic-high control range from 3.3 to 24 Vdc
• Two 25 mA open-collector outputs
• Two single-pole relay contacts
• 60 W maximum switching power
• 0° C to 55° C ambient operating range

What Makes It Different

Unlike a control relay described only by a single input event, the ST-LCR3 specifically supports pulse generation at both boundaries of a logic signal: its start and its end. It also makes both relay-contact and open-collector pulse outputs available. That combination provides distinct interface options for switching loads, operating indicators, or controlling compatible slave LCRs without changing the supported input-voltage range.

The supplied product resources include a PDF specification sheet, American DXF engineering functional-block and panel diagrams, and high-resolution TIF images. These resources support planning and documentation for integration.

Final Assessment

The RDL ST-LCR3 is a focused control component for systems that require separate pulse responses when a logic signal starts and ends. Its active-high or active-low inputs, 3.3 to 24 Vdc control range, dual 25 mA open-collector outputs, and two single-pole relay contacts define its practical role clearly. For installations using switches, pushbuttons, or logic circuits and requiring both electronic and relay-contact pulse interfaces, the ST-LCR3 provides the specified functions in a single model. Confirm the connected loads, control levels, and ground-referenced 24 Vdc supply against the published limits before installation.