Adding a Second Remote to Your Battery Train Horn (and Replacing the Fob Battery)

Every battery train horn we ship comes with one wireless remote. Two drivers, two vehicles, or a fob that lives in a jacket you never wear are all good reasons to add a second. Here is how the receiver stores more than one remote, how to pair the new one in about a minute, and what to do when the fob goes quiet because its little battery is done.

Can Two or Three Remotes Run One Horn? Yes

The remote system on these horns is a 433 MHz radio link. Inside the fob, an encoder chip from the EV1527 family sends a 24-bit message: a 20-bit transmitter ID set at the factory plus 4 bits that say which button you pressed. Twenty ID bits give 1,048,576 possible transmitter codes, which is why two fobs from the same batch never fire each other's horn by accident.

The receiver board in the horn is a learning receiver. It keeps a small memory of transmitter IDs, and any fob whose ID is stored there fires the horn. Pair a second fob and the receiver holds two IDs. Pair a third and it holds three. The maker of a common receiver board says it plainly: additional transmitters with different IDs can be learned and stored on top of the first. The exact ceiling varies by board, but it is far beyond the two or three fobs most owners ever want.

That is what the Extra Remote Control add-on is for. Every kit already includes one remote. Add this item to the cart with your horn and the order ships with two, and you can raise the quantity if you want a fob for every driver.

Pairing the Second Remote, Step by Step

If your first remote came factory-paired, this is your first time touching the learn button. The sequence below is the standard one on 433 MHz learning receivers and matches our lost-remote pairing guide. Keep the sheet that came with your horn in case your board's flash pattern differs.

1. Power the horn. Click a charged tool battery into the base. The receiver only listens when the horn has power.
2. Put a fresh cell in the new fob. A fob that sat in a warehouse can arrive with a tired battery, and a weak transmitter is the number one reason pairing fails.
3. Find the learn button. Open the control box and look for a small button next to an LED on the receiver board, sometimes labeled LEARN or CODE.
4. Press it once. The LED lights to show learning mode. One press is momentary mode on most boards: the horn sounds while the fob button is held and stops when you let go, which is what you want for a horn.
5. Press the new fob's button once. The LED flashes three times on common boards to confirm the ID is stored.
6. Test both remotes. Fire the horn from the old fob, then the new one, up close and then from across the driveway. Pairing a second fob does not erase the first.

One mistake to avoid: do not press the learn button several times while fumbling for the fob. On many boards two presses selects a latching mode where one press turns the horn on and the next turns it off, and eight presses wipes the memory. If you land in the wrong mode, wipe and re-pair.

The whole job takes about a minute with no wiring anywhere in it. If you are also mounting the horn for the first time, our battery train horn install guide covers placement, brackets, and optional hard-wiring on top of the remote steps.

Mixing Remote Types on One Horn

The receiver stores IDs, not remote models, so nothing stops you from pairing one compact fob and one long-range transmitter to the same horn. The small fob rides on the keyring, and the long-range unit stays in the truck for the far end of a field or a boat launch.

Remote	Rated range	Battery inside	Best for
Standard fob (ships with the horn)	About 160 ft on the Extreme Series	Small 12V or 3V cell, see below	Keyring, daily use
Remote Control (300ft)	300 ft	Small 12V or 3V cell, see below	Parking lots, job sites
Long-Range Remote (2,000ft)	Up to 2,000 ft line of sight	9V, pre-installed	Farms, launches, race starts
Industrial Waterproof Remote	Up to 260 ft	Sealed unit	Boats, plows, gloves

Range numbers are open-air, line-of-sight figures. Steel bodywork between the fob and the receiver antenna shrinks them fast, which is a separate problem from pairing. Our 433 MHz range and dropout guide covers antenna placement and interference, and the 300 ft vs 2,000 ft comparison helps you decide whether the long-range unit should be your second remote.

On the flagship Extreme Series Train Horn for Milwaukee® 18v Battery, the included remote is rated to about 160 feet and the long-range option stretches that to 2,000 feet, while the horn keeps running off whatever M18™ pack you already own.

Which Battery Is Inside the Fob

This is the question that fills our inbox, and the honest answer is: open the case and read the print on the cell, because compact 433 MHz fobs use one of two very different batteries.

Cell	Voltage	Size	Capacity	Also sold as
A23	12V alkaline	10.3 mm x 28.5 mm	About 50 to 55 mAh	23A, MN21, 8LR932, V23GA
A27	12V alkaline	8 mm x 28.2 mm	About 22 mAh	27A, MN27
CR2032	3V lithium coin	20 mm x 3.2 mm	About 225 mAh	DL2032, ECR2032
9V (long-range remote)	9V alkaline	Standard rectangular	About 550 to 600 mAh	6LR61, PP3, MN1604

Compact garage-opener style fobs like the one that ships with most horns are typically built around a 12V cylindrical cell, the same one in car-alarm remotes and wireless doorbells. An A23 is a stack of eight tiny LR932 button cells in a tube slightly smaller than a AAA. Its skinny cousin the A27 is also 12V but only 8 mm across with less than half the capacity, and the two are not interchangeable: an A27 rattles loose in an A23 bay, and an A23 will not fit an A27 bay at all. Some fob housings instead take a flat 3V CR2032 coin cell. Match the code on the old cell and you cannot go wrong.

The long-range transmitter is the outlier. Its external antenna and bigger transmitter need more than a coin cell delivers, so it runs on a standard 9V alkaline that ships pre-installed. A 9V holds roughly eight times the energy of an A23.

Replacing the Fob Battery

A weak fob rarely dies all at once. Range shrinks first: you walk closer, press twice, and one day the LED barely glows. Alkaline A23 cells are typically rated for three to five years of shelf life, and coin cells in key fobs are commonly replaced every two to five years, sooner if the button gets mashed in a pocket. Here is the swap:

1. Open the case. Most fobs split along the seam. Use a fingernail or plastic pry tool at the notch near the keyring hole; a few use a small Phillips screw on the back. Avoid a metal screwdriver on the seam.
2. Note the orientation. Cylindrical cells sit in a spring clip with plus and minus marked on the board. Coin cells usually sit plus side up. Take a phone photo before pulling the old cell.
3. Swap the cell. Hold the new one by the edges. Skin oil on the flat faces of a coin cell raises contact resistance over time.
4. Check the LED. Press the button before closing the case. A bright, steady flash means the transmitter is happy.
5. Snap it shut and test range. No re-pairing is needed: the transmitter ID lives in the chip, not the battery, so a battery swap never un-pairs a fob.

One safety note for coin-cell fobs. The U.S. Consumer Product Safety Commission counted 27 deaths and an estimated 54,300 emergency-room injuries from swallowed or inserted button and coin batteries between 2011 and 2021, and a swallowed cell can burn through a child's esophagus in as little as two hours. Under Reese's Law, coin cells sold in the U.S. now come in child-resistant packaging, and the CPSC's mandatory standard requires battery compartments that need a tool or two simultaneous motions to open. Keep spare cells out of reach while you work, and tape the faces of a dead coin cell before it goes in the trash.

Holding the button down does not help, either. Under 47 CFR 15.231, the FCC rule these fobs operate under, a manually operated transmitter must stop transmitting within five seconds of release, so a stuck button in a pocket is a battery drain, not a range boost.

When to Wipe the Receiver and Start Over

Adding a remote never requires erasing the old ones. But in three cases you want the receiver to forget everything and learn only the fobs you hold:

• A fob was lost, not replaced. The receiver keeps obeying every ID it has learned, so whoever finds the old fob can fire a 150 dB horn in your driveway.
• You landed in the wrong mode. If a pairing attempt put the receiver in latching mode, the horn stays on after a press. Wipe and re-pair in momentary mode.
• You bought the horn used. The previous owner's fobs are still in memory. Clear it on day one.

On common learning receivers the wipe is eight consecutive presses of the learn button. The LED flashes seven times to confirm, then you wait about two seconds and run the pairing steps for each remaining remote, one at a time. Every fob you own has to be re-learned after a wipe, including the one from the box. If a horn ever fires on its own, our stuck-on horn guide starts with this same sequence.

FAQ

Will a second remote drain the horn's tool battery faster?

No. The receiver draws the same small standby current whether it has one ID or five stored. Standby drain is covered in our standby drain guide.

Can I pair one remote to two horns instead?

Yes. Run the learn sequence on each horn's receiver with the same fob, and one button fires both. The Industrial Waterproof Remote is sold specifically to pair with multiple horns at once. Every paired horn within range fires together.

Do I need to re-pair after changing the fob battery?

No. The transmitter ID is fixed in the encoder chip. Swap the cell, press the button, and the horn answers exactly as before.

Can I use a garage-door or car-alarm remote as my second remote?

Only if it is a fixed-code 433 MHz transmitter. Most modern garage and car fobs are rolling-code, which a fixed-code learning receiver cannot store.