The Circuitron SD-3 is an electronic signal driver for model railroaders building layouts with single searchlight-style LED signals. It controls bi-color or tricolor signals and produces red, green, and amber aspects.
Key details
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Application: HO and N scale model railroad layouts
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Material: 2-inch by 3-inch printed circuit board
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Compatibility: Single searchlight-style, 2-lead or 3-lead, bi-color or tricolor LED signals
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Compatible signal brands: Oregon Rail Supply, Tomar, Sunrise Enterprises, ISS, and others
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Input: 10–18 volts AC or DC
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Control options: Single-pole, 3-position switch or automatic detection circuits such as Circuitron BD-1, BD-2, and BD-3
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Important detail: Two SD-3 units are required for double-head signals. The SD-3 does not drive 3-lamp signals; see the SD-1 for that application.
Signal control for layout builders
Bi-color LEDs use red and green chips to create an amber appearance, with hue adjustment available on the SD-3. Other detection circuits may also be used when they provide a logic-low ground or negative output.
Related information
For manufacturer information, visit Circuitron Electronics. For related layout components, browse Train Layout Construction.
