Lineman Apps Built by a Lineman: XFMR Lab & URD Training Apps

Lineman's Reference - XFMR Lab

Overhead Transformers & Banking

2.0

Trusted by 30,000+ users since 2021. Get unlimited reps wiring banks without needing a transformer or training yard.

★ 4.1 / 128 ratings Price $19.99 · One-Time

16 labs, tap changers on all 9 banks, real fault behavior

Sandbox: build any bank, watch vector wheels and voltages react live

XFMR Training: from "What's a transformer?" to wiring your first bank, these guided lessons are written in a way we can all understand and are easy to follow along. Read lesson 1 free →

Death Traps: The transformer scenarios that get linemen injured or worse. Walk through them on your phone instead of in the bucket

Lab select screen listing closed and open bank labs — 16 wiring labs to choose from

Death Traps warning: a floating tank ground can be lethal — Death Traps

XFMR Training lesson list — XFMR Training

Want the app to match your utility's standards? 2.0 ships with customizations you can share device-to-device. Request a customization →

Lineman's Reference - URD

Underground Residential Distribution

Underground distribution made hands-on. Switching, troubleshooting, and the scenarios apprentices actually hit in the field.

Price $9.99 · One-Time

Use a shotgun stick, feed-thrus and phasing sticks to learn Underground Residential Distribution

Troubleshoot URD outages: isolate, test and ground cable sections and padmounts

Hi-potting, cable isolation, and switching training; step-by-step

An open padmount transformer in URD — Work inside three-phase padmounts

Underground loop switching map — Complex loop switching

Checking voltage with the meter in URD — Troubleshoot padmounts

▶ 2-Min Demo

The One-Man Show, Run by a Journeyman.

I'm Trent Carlock, a ticketed JL who still runs a bucket every day. Digital Apprentice is a one-man show: I build these apps in my spare time with nearly a decade of troubleshooting, building and maintaining overhead and underground distribution lines.

XFMR Lab is the only pocket-sized transformer lab simulator available to everyone in the industry that's teaching transformer wiring, banking and theory. Quiz yourself and your crew on common transformer knowledge and niche situations.

URD jump-starts underground apprentices. From explaining the basics of underground loops, to normally open and normally closed switch positions, to hi-potting and isolating faulted cable sections, Lineman's Reference - URD takes potentially-confusing concepts and procedures and turns them into clear, digestible labs that a first-day hand can complete.

Since I first launched XFMR Lab in 2021, over 30,000 linemen and apprentices have used these apps to study and practice before stepping up to energized situations. Linemen use them as quick field references when they hit a situation they haven't seen in a while. Apprenticeship programs and power companies use these apps to train their employees and often install them on company-provided phones and tablets.

These aren't calculator/diagram apps. They're fully interactive apps that require you to manually wire banks, pull elbows, check voltage, open/close/blow fuses, and restore power to customers. A calculator gives you a number. These apps teach you how and why.

Recognized at

2022 International Lineman's Rodeo · Kansas City 1st Place · Training Systems 2nd Place · Top Tools of the Trade

The Mission

I want to change the game for learning in linework. Making the learning tools apprentices and students need widely available and affordable, with real-time affirmation and correction.

Trent · Digital Apprentice LLC

misc REsources

I'll be periodically uploading educational videos, 3D-printable tools, and other free resources I come up with, here.

Free Lesson

What Is a Transformer?

Lesson 1 of XFMR Training, free and no signup: the primary and secondary sides, the two coils, turns ratio, tank grounds, and polarity. It's the exact lesson from inside the app, written by a journeyman lineman.

Read Lesson 1 →

3D-Printable

The Hand-Tie Speed-Roller

Partnership with Poletop: Free STL.

Infill: Gyroid 30%
Supports: On
Filament: PLA+

⚠ SUPER GLUE THE HANDLE IN PLACE!

↓ speedRoller.stl · 3.3 MB

Educational

"The neighbors have power, so why don't I?"

Video thumbnail: troubleshooting why one house is out when the neighbors have power

Real troubleshooting, explained the way you'd hear it on the job. More videos on the channel.

YouTube Channel ↗

Beta Testing Sign-Up.

Want new features before everyone else, or want to tell me what's broken? Sign up below and I'll send you an invite when BETA testing is available.

Common Questions.

Do the apps work offline?

Yes. Once installed, everything runs locally on the device with the exception of optional iCloud sync (to maintain your progress across devices).

One-time purchase or subscription?

One-time purchase, full stop. Pay once, own it. No monthly fee, no annual renewal, no in-app paywalls. Updates are included.

What if I get a new phone?

Sign in with the same Apple ID or Google account on your new device and re-download free. Your purchase is tied to your account, not the hardware. Switching platforms (iOS ↔ Android) means buying again, since the two stores don't share purchases.

Is this just a kVA calculator or transformer sizing app?

No. XFMR Lab is a full transformer banking simulator. The kVA math, standard transformer sizes, and primary/secondary voltage tables are baked in for reference, but you don't compute on a slider. You wire the bank, energize it, and verify with live voltage, ohm, and rotation meter readings. Single-phase pots, three-phase banks, open and closed deltas and wyes, customizable quizzes, troubleshooting scenarios. Calculator apps give you a number. XFMR Lab and URD teach you how to do it in the field.

What's the difference between XFMR Lab and URD?

XFMR Lab covers Overhead Transformers: banking, voltage and rotation checks, safe work practices. URD covers Underground Residential Distribution: pad-mounts, switching, cable isolation, hi-potting, and the troubleshooting scenarios you actually see in the field. URD secondary troubleshooting is coming soon.

Who built these apps?

I did. I'm Trent Carlock, a journeyman lineman who still runs a bucket. I build these apps under my company, Digital Apprentice LLC, and every scenario, every troubleshooting lab, and every niche situation comes straight from time on the job, not from a developer guessing at what the trade needs. Although admittedly I have read a textbook or 2.

Are they for apprentices or journeymen?

Both. Apprentices use them to learn and get reps safely before stepping up to the real thing. Journeymen use them as a quick field reference when they hit a configuration they haven't worked in a while.

Get In Touch.

Questions, bug reports, customization requests, or want these apps on your company phones? It's just me on the other end, and I usually reply quick.

✉ Send a Message

Prefer plain email? info@digitalapprentice.net works too.

The Poletop Shop

Poletop

Stickers, shirts, and gear for hands who have a sense of humor - the lighter side of the trade.

Visit poletop.shop

Apps Created by a Lineman,For Linemen and their Apprentices.