Quad DCC Function Decoder with Integrated Transponder. Four 125mA (250mA peak) function output for lights or other functions; Functions can be turned on/off using F0-F12; Supports both 2 digit and 4 digit addressing; Programmable from DCC compatible equipment; Configurable Strobe feature lets you simulate flashing lights like FRED,Strobes, Mars Lights, etc. on the yellow and white leads; Standard On/Off Function operation available on green & violet leads; Compatible with Digitrax DCC Transponding Systems; Approximate size: 0.461” x 0.31” x 0.161” (11.7mm x 7.8mm x 4.1mm)

Control signals on your layout manually with any LocoNet Throttle and Command Station or automatically with detection and compatible computer software such as RR & Co. and WinLok. Drives up to 32 signal heads with popular LED signal types. Simple modular wiring. 16 inputs, 8 Control lines for local turnout control, 8 occupancy sensor inputs. DC or DCC controlled layouts.
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Sets of 3 Signal Masts that can be used as Signal Mast bases in any scale or can be painted and detailed as N-scale signal masts.
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Materials for making 2 Signal Driver Cables for SE8C. Includes 20 feet of 10-wire ribbon cable and 8 Ten pin connectors.
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Under layout mounting hardware for Signal Driver Cables and sockets. 6 metal signal straps and 6 signal spacers.
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Terminal strip board with resistors installed for easy installation of most brands of LED type signal masts.
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Quad Occupancy Detector, Replaces BD1.
Cost Effective occupancy detection for 4 detection sections. Outputs for panel mounted LEDs to display occupancy. Detects any powered locomotive. Detects un-powered rolling stock equipped with resistor wheel sets. Can transmit occupancy information to your LocoNet System using DS54 or SE8C (sold separately).
Using Team Digital SIC 24 with Digitrax BD4 (external link)
Note - "I had problems with the  BD4 - I am running this as standalone and could not get it to indicate anything. I found on the internet a tip for adding a ground wire from DS pin 2. This info is missing from the Digitrax tech sheet."

LocoNet Occupancy Detector, Replaces BDL162
Cost Effective occupancy detection for 16 detection sections. Outputs for panel mounted LEDs to display local occupancy & power zone status. Can be connected to LocoNet to transmit occupancy information to your LocoNet System. Detects any powered locomotive. Detects un-powered rolling stock equipped with resistor wheel sets. Improved Digitrax Transponding in 8 zones by adding 2 RX4 Transponder Receivers (sold separately). Ops Mode Read Back allows you to read back CV Values on the mainline using Transponding.

Remote Sensing Diode Board for BDL16
Remote sensing diode board for 2 remote detection sections for use with BDL16. Makes wiring a really big layout much simpler because you don't have to run heavy wires to remote locations to set up detection.

4 block transponding receiver for BDL16.

Not yet released. 8 block transponding receiver for BDL16.

Transponding device for locomotives, rolling stock & cabooses with lighting output for coach lights or FRED. Can be added to most existing DCC decoder installations. Decoders fitted with TL-1 will run on other DCC systems but transponding will only be available on Digitrax LocoNet systems fitted for transponding. Transponding devices can be installed in units without decoders, too! Dimensions: 0.375" x 0.385".