Trine Electric Strike for an Apartment Building Intercom Entry

Posted by Kent on 29th Jul 2026

By Kent · Lock Depot Staff Writer

The buzz-in door at an apartment building is the most-cycled piece of hardware in the whole property. Every tenant, every guest, every delivery, all day. When the strike on that door quits, the intercom is useless and the manager's phone rings all night. The fix is usually a Trine electric strike, and Trine has owned this exact job for decades because they build a strike that survives the abuse.

How the intercom entry actually works

A tenant hits the button in their unit and the intercom sends power to the strike at the front door. The strike releases for a couple of seconds so the visitor can pull the door open, then it locks again. Nothing fancy. The strike is the muscle at the end of that signal, and it is the part that wears, because it takes the load of that door slamming shut a few hundred times a day.

Fail-secure, and why it is the right default here

This is the single decision people get wrong, so get it right. A fail-secure strike stays locked when the power is off. A fail-safe strike unlocks when the power is off. For an apartment entry you almost always want fail-secure. If the power blows, you want the building's front door to stay locked, not swing open to the street. Tenants still get out from the inside anytime, because the exit side is always free by law and by the door's own lever. Power failure locks the strangers out, not the tenants in. The standard Trine strikes are fail-secure for exactly this reason.

From the counter: match the voltage to your intercom before anything else. Old buzzer systems run on AC; newer access panels often run DC. The 1001-2B is a 14-24V AC/DC strike that runs on either, which is what you want when you are not certain what the existing system puts out. Put a DC-only strike on an AC buzzer and it hums, gets hot, and dies. When in doubt, order the AC/DC model.

Measure the cutout before you order

An electric strike drops into a pocket in the frame, and the pocket size matters. A 4-7/8" strike will not sit in a frame cut for a 5-7/8", and vice versa. If you are replacing a dead strike, pull it, measure the faceplate and the cutout, and match the dimension. The 5-7/8" x 1-1/4" is the common ANSI size on a lot of commercial frames, but common is not the same as certain. Measure your frame. A strike that does not fit the cutout means grinding the frame, and now a fifteen-minute swap is an afternoon.

Common questions

Fail-safe or fail-secure for an apartment entry?

Fail-secure. Power loss keeps the front door locked. Tenants always exit freely from inside; only strangers are kept out.

AC or DC?

Match your intercom. Old buzzers are usually AC, newer panels DC. If unsure, order the AC/DC model that runs on either.

How do I get the size right?

Pull the old strike and measure the faceplate and cutout. 5-7/8" x 1-1/4" is common but confirm your frame before ordering.

Lock Depot stocks the Trine electric strike line in AC, DC, and AC/DC, fail-secure, in the common frame sizes, in stock. Start at the Trine hub, or read the companion piece on choosing a strike for an access-control retrofit: Which HES Electric Strike for an Access-Controlled Metal-Frame Door. Or call 877-365-5625 with your voltage and your cutout size.