Viking Electronics LDB-2 Ring and Loop Detect Board
Overview
The Viking Electronics LDB-2 is a compact ring and loop detect board that converts telephone line activity — ringing voltage or loop current — into dry contact closures. If you need to trigger an external device (door access, alert light, relay-driven automation) whenever a phone line rings or goes off-hook, the LDB-2 provides that bridge without complex programming or proprietary middleware. It ships with a 120V AC to 12V DC power adapter included, so it arrives ready to wire. The LDB-2 (often searched as LDB 2) measures just 1.875" x 1.2" (47.6mm x 30.5mm) — small enough to tuck into an existing enclosure alongside other telecom or access control hardware.
Key Features
- Dual Detection Modes — Ring and Loop: The board detects both ring voltage (inbound call) and loop current (off-hook state), giving you two independent trigger conditions from a single device. This means one LDB-2 can cover both an alert-on-ring and an alert-on-answer scenario without doubling your hardware.
- Contact Closure Output: Outputs are dry contact closures, the universal handshake for third-party integration. Whether you're driving a door strike, triggering a relay board, or feeding a security panel zone input, contact closures require no voltage matching or protocol negotiation.
- Included 12V DC Power Adapter: The 120V AC to 12V DC adapter ships in the box — no separate power supply order needed. The board also exposes auxiliary 12V DC output terminals, which can power a downstream device directly and eliminate a second wall-wart in low-current auxiliary applications.
- Compact Form Factor for Tight Installs: At 47.6mm x 30.5mm, the LDB-2 fits inside most telecom backboxes, rack-mounted enclosures, or custom panels. Mounts via two #4 screws (not included) or the included foam tape for tool-light installs on flat surfaces.
- Simple Mechanical Mounting: Foam tape is included for fast deployment on flat surfaces; screw mounting provides a permanent, vibration-resistant installation where the board may be bumped or accessed regularly.
- Analog Line Compatible: Designed for standard analog phone lines and FXS ports — the signal types common in legacy PBX integrations, elevator phones, and entry phone systems where telephone line activity needs to drive external hardware.
Integration and Compatibility
The LDB-2 targets analog telephone environments — POTS lines, FXS ports on VoIP gateways, and legacy PBX analog extensions. Contact closure outputs integrate directly with access control panels, security system zone inputs, or any relay-accepting device. The auxiliary 12V DC output terminals are useful for powering a companion device (small relay module, indicator light) without adding a separate power supply, provided the current draw stays within the board's rated capacity. If your deployment requires detection on a digital or IP-based line, the LDB-2 is not the correct tool — it operates exclusively on analog loop/ring signals.
Frequently Asked Questions
Q: What does the LDB-2 actually detect — ring, off-hook, or both?
A: Both. The LDB-2 detects ring voltage (inbound ringing) and loop current (off-hook/line in use), providing contact closure outputs for each condition.
Q: Does the LDB-2 include a power supply?
A: Yes. A 120V AC to 12V DC adapter is included. The board also provides auxiliary 12V DC output terminals for powering a connected downstream device.
Q: What mounting options are available?
A: The LDB-2 mounts via two #4 screws (not included) or foam tape (included). The board measures 47.6mm x 30.5mm, fitting inside most standard telecom enclosures.
Q: Is the LDB-2 compatible with VoIP or digital phone lines?
A: The LDB-2 is designed for analog telephone lines and FXS ports. It is not intended for direct connection to digital or IP-based lines.
Q: What type of output does the LDB-2 provide?
A: Dry contact closures, triggered on ringing or off-hook conditions. These integrate with access control panels, relay boards, security zone inputs, and similar hardware.
The LDB-2 fills a specific integration gap I run into regularly: you have an analog phone line — an elevator cab phone, a door entry intercom, a legacy PBX extension — and you need that line activity to drive something external. The LDB-2 handles both ringing and off-hook detection on a board that's barely 47.6mm x 30.5mm, which means it disappears into whatever enclosure you're already using.
Technical Highlights:
- Dual-condition detection: Ring voltage AND loop current on one board — you get contact closures for both inbound ring and active call state, which covers most trigger-on-event use cases without stacking two separate devices.
- Included 120V AC to 12V DC adapter: Ships ready to power; the auxiliary 12V DC output terminals on the board let you feed a small downstream device without adding another supply to your panel.
- Compact footprint — 47.6mm x 30.5mm: Fits inside standard telecom backboxes and rack enclosures alongside other hardware; foam tape mount means zero drilling in retrofit scenarios.
Deployment Considerations:
- Screw mounting requires #4 hardware — those are not in the box, so have them on the truck for permanent installs where foam tape won't do.
- This board is analog-only; if the FXS port you're connecting to is on a SIP gateway running non-standard loop signaling, verify ring voltage and loop current levels match conventional analog spec before committing to the install.
Best fit for elevator phone monitoring and legacy entry intercom integration where analog line activity needs to feed a contact-closure-driven access control or alert system — exactly the kind of retrofit where a small, self-powered board like the LDB-2 saves significant panel space and wiring complexity.
