SDC 423U Electronic Timer Exit Switch
Overview
The SDC 423U is a 24VDC electronic timer designed for door access control installations where you need adjustable egress delay or timed relay control. It mounts on a single-gang wall plate and provides a 1–60 second adjustable dwell time — crucial when integrating with electronic locks that require a time window to disengage before the door resets. The DPDT (double-pole, double-throw) relay contact rated 3A @ 30VDC handles standard solenoid strikes and magnetic locks without additional interface modules.
Compatibility
The 423U works with any door strike or magnetic lock system operating on 24VDC. It integrates into SDC's 420 series push-button switch line and functions as a timed release module for exit-control scenarios. The unit accepts 24VDC input (±10%) and outputs a dry relay contact — compatible with both momentary and continuous-duty solenoid applications. If your installation uses a separate access control reader (keypad, proximity, or networked controller), this timer can be wired in series with that reader's relay output to add dwell-time control downstream.
Installation Notes
Single-gang wall mount on standard electrical boxes. Faceplate is 20-gauge stainless steel (2 7/8" wide × 4 1/2" tall) — suitable for indoor environments where corrosion resistance matters. Pre-wired with 6-inch, 20 AWG leads for connection to your strike or lock circuit. The timer adjustment (potentiometer) is internal; set the dwell time during commissioning — no field reprogramming after installation without opening the faceplate. Ensure 24VDC supply is stable within ±10%; voltage sag or ripple will affect timing accuracy. Standard pushbutton signage reads "PUSH TO EXIT" with green/red lens options for visual feedback.
What's in the Box
- 1x SDC 423U Electronic Timer unit
- 1x Single-gang stainless steel faceplate (2 7/8" × 4 1/2")
- 6-inch pre-wired leads (20 AWG)
