Audio Overlay Best Practices

Relevance: This app note applies to the Z3 Plus, PD8 Plus module and the discontinued ZEPICIII, PD8 module.

Purpose: The purpose of this App note is to emphasize long held rail industry best practices for installing audio overlay track circuits. It is useful to periodically review this material to insure proper installation and maintenance for audio overlays whether installed by railway personnel or 3rd party contractors.

  1. Insure that the operating frequency of the audio overlay is compatible with the operating frequency of all other
    equipment on the same track and neighboring tracks, if applicable.

  2. Use properly rated primary surge protection and ground rods. See relevant AREMA specifications.

  3. Periodically inspect primary surge protection for wear due to surge activity. Reduced effectiveness of primary protection can expose secondary protection to excessive surge levels resulting in equipment failure.

  4. Use twisted # 6 bond strand for track wires between rail connections and the overlay unit. Audio overlays are generally used in switch unlock, DED and AEI presence detection applications. As such, these products may be located near crossings and within signal system circuits. If a short circuit were to occur in the track wires or surge protection or house wiring, the signal system would be put to stop due to the low resistance of #6 track wires, calling attention to the affected area.

  5. Monitoring diagnostic data provided by DED and AEI systems will facilitate the prompt and efficient maintenance of audio overlays.

  6. The product user manuals for these products have been updated to include a simple shunt test to work hand in hand with best practice installation methods detailed in this app note.

  7. Check often for current user manuals, installation tips and troubleshooting procedures.


Z-Tools is a PC based application that was specifically designed with simplifying installation and maintenance of Zukinut products. Remote access allows functions such as firmware updates, calibration data capture, remote calibration and product troubleshooting. The Graphical User Interface is product sensitive and simple to use.


ZEPIC5 Distance-To-Couple

  “Keep Your Distance”

The ZEPIC5-DTC represents a major technological advancement in Distance to Couple systems for railroad classification yards. The system employs proprietary signal processing algorithms used for frequency to distance conversation, speed calculation and determination of direction. The system provides isolated RS485 communication (half or full duplex) to interface to yard computers allowing for remote access of all internally processed data.

Provides distance to couple, speed and direction data.

Self-contained unit provides all necessary data processing, track drive and communications.

Diagnostic troubleshooting codes with built-in push buttons and display.

All user configurations stored in non-volatile memory.

Compatible with Z-Tools

ACDz Yard Track Circuit

The ACDz is a new generation of the ACDC type track circuit for yard applications. Unlike its predecessor, the ACDz uses hard wire terminations in place of diode shunts and can work with insulated joints, but does not require them. The transmitter drives the track, via 2-wire connection and can be configured as an end-to-end or center fed circuit. This new approach allows the ACDz to provide the same operational logic as an ACDC circuit without the need of a railroad relay.

The ACDz provides 2ea dry contact relay outputs, one for local control of a switch machine and the other for occupancy indication to the yard computer.

ACDz is compatible with Z-Tools and Z-Stick.

Product Bench Test Procedures Added

Zukinut Technical Support has published product tests procedures for the
Ze2500 presence Detector, the ZEPIC4 HFTC and the Z3 Plus 2-Wire Audio Overlay.
These procedures are tailored for use in the signal shop and greatly simply the
evaluation of a units operational status.
Log-in to the Zukinut Customer Support section of and go to User manuals.

ZEPIC6 Clearance Track Circuit

The ZEPIC6 is a new and innovative approach to solving the most challenging clearance track circuit applications.

This product provides two independent track drive outputs with the provision of sub-dividing the respective CTC into 2 circuits. In total, a single ZEPIC6 is capable of providing 4ea track circuits. The empty circuit limits are defined by a hard wire shunt located at the entering end and a Zukinut supplied inductive shunt at the DTC end. Using a center fed arrangment, the ZEPIC6 can pick cleared circuits behind a moving car, allowing faster access to diverging routes of following moves.

Diagnostic troubleshooting codes with built-in push buttons and display.

All user configurations stored in non-volatile memory.

Compatible with Z-Tools

Z-Tools Z-Stick Installation and Use Guidelines

We are beginning the roll out of our newest products, Z-Tools and Z-Stick. These tools are communications based products used to remotely interface and control many of our products. Remote functions include, upload and download of product configuration and firmware, remote calibration and monitoring.

We have posted introductory videos and installation app notes in the User Manuals section of our customer service site.