Logic Controlled Relay-Latching

Ideal Use Cases

The RDL ST-LCR2 is a logic-controlled, alternate-action switching module for applications in which a switch, push-button, logic circuit, or open-collector output must operate relay contacts. Its double-pole, double-throw relay is suited to control arrangements that require two contact sets from one control action. The module can also add contacts to an existing control signal. A remote push-button or switch can operate the relay through the SLAVE input, while dedicated voltage inputs support activation from compatible DC control circuits.

Why Choose This Model

The ST-LCR2 combines several control methods in one compact relay module. The SLAVE terminal activates when connected to ground, allowing a remote switch or push-button to control the relay directly. It can also receive an open-collector output from other equipment, including RDL switching STICK-ON modules with suitable open-collector outputs. For voltage-based control, the 5 V+ terminal accepts 3.5 to 12 Vdc, and the 24 V+ terminal accepts 12 to 35 Vdc. This range of input options makes the module adaptable to multiple control-signal formats without changing its DPDT switching function.

Installation and Integration

The module requires a ground-referenced 24 Vdc supply at 50 mA, based on a maximum 20 mA load at the SLAVE output. The recommended power supplies are the PS-24AS for the USA and the PS-24AX for international use; the power supply is not included. When using the SLAVE input, relay activation is achieved by connecting the input to ground through a remote switch or push-button. An open-collector output from other equipment can operate the same input when that output is on.

The 5 V+ input provides alternate-action control. A high pulse followed by a low level turns the relay on; the next high-to-low pulse turns it off. The 24 V+ terminal accepts a 12 to 35 Vdc signal to activate the control circuit. An open-collector SLAVE output rated at 25 mA is available for indicators or additional slave LCR modules. The enclosure measures 0.7 inches high, 3 inches wide, and 1.6 inches deep, supporting integration where available space is limited.

Performance Highlights

The switching section uses double-pole, double-throw contacts and has a maximum switching-power specification of 60 W, listed with 220 Vdc, 125 Vac, and 2 A ratings. The ambient operating range is 10° C to 55° C. Its open-collector output provides up to 25 mA for driving an indicator or slave LCR. Power demand is specified as ground-referenced 24 Vdc at 50 mA when assuming a maximum 20 mA load at the SLAVE output. These ratings provide concrete parameters for matching the relay to the intended control circuit and switched load.

What Makes It Different

The defining capability of the ST-LCR2 is its combination of alternate-action switching and direct SLAVE control. A maintained remote switch can turn the relay on while that switch is on, whereas the 5 V+ input can toggle the relay state through successive high-to-low pulses. Open-collector compatibility also allows the relay to respond to logic equipment without requiring a conventional switch contact at the control point. The DPDT relay adds two-pole switching to any compatible control signal, and the 25 mA open-collector output can extend the control action to an indicator or another LCR module.

Final Assessment

The RDL ST-LCR2 is a focused solution for adding DPDT relay contacts and alternate-action behavior to switch, push-button, logic, or open-collector control systems. Its grounded SLAVE activation, two DC voltage-input ranges, 25 mA slave output, and clearly specified 24 Vdc power requirement provide several practical integration paths. For installations requiring compact relay switching with both direct and toggled control behavior, the ST-LCR2 offers a defined set of control and output functions in a 3-by-1.6-inch footprint.