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What Is A Pinball Knocker?

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Few objects are able to conjure up such intense nostalgia the way a pinball machine does. The cacophony of noise that emanates when you turn one on is a rush in and of itself, but no sound is more iconic than that of a pinball knocker. However, if you were born after the decline of traditional arcades, you may not know that sound – or that it is even a part of the pinball machine.

What is a pinball knocker?

A pinball knocker is a small solenoid-fired piston inside the machine which knocks against a mounting bracket, creating a loud “thwack” sound, in order to indicate when a high score has been beaten or that a free game has been won. However, not all pinball knockers are physical, as newer machines will use a prerecorded audio file in its place.

If you have ever wondered what that loud sound is when you win a free game in pinball, that is a pinball knocker!

For those who remember their days in the arcade fondly, the smack of a pinball knocker ranks among the all-time most satisfying sounds and is a crucial part of the playing experience. There are many different types of knockers and finding the specific sound associated with a particular machine is often a major point of focus for collectors and enthusiasts.

To learn more about pinball knockers you can keep reading or watch the video below.

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How Do Pinball Knockers Work?

Pinball knockers have been a staple of the game since its inception. While most players will listen excitedly for the loud smack, which signifies their victory, blissfully ignoring the inner workings of the machine, you might be curious to know how a knocker actually works.

Having this knowledge will be especially helpful if you are trying to restore an old pinball game or get your hands on a new one.

For the most part, a pinball knocker assembly will be put together using about seven basic components. A list of these components is provided below.

  1. The Coil Sub-Assembly: This piece houses the plunger and contains the solenoid firing electronics.
  2. The Coil Retaining Bracket: The retaining bracket keeps the coil sub-assembly in place and separates it from the rest of the unit’s housing.
  3. The Coil Plunger Assembly: The plunger is the rod that is fired out of the coil sub-assembly.
  4. The Plunger Retention Spring: Most relatively modern knockers do not use them, but older models will. A small spring is placed over the coil plunger and functions to keep it in retention.
  5. A Rubber Grommet/Head: At the end of the coil plunger will be a rubber grommet or plastic stopper head, which is the portion that is fired into the rear panel of the machine, or into the face of a metal bracket, creating the iconic knocker sound.
  6. A knocker cable: This is the cable that connects the pinball knocker unit to the motherboard of the table.
  7. The Mounting Bracket Assembly: And finally, everything is held together with a mounting bracket assembly, along with a few screws, which allow the knocker unit to be mounted inside the machine.

Like most things in modern times, pinball knockers have been manufactured by many different companies over the years, and there are plenty of variations in their exact design.

But the way they function never changes.

When activated, a quick pulse of electricity is sent through a solenoid coil, creating an electromagnetic field for a split second, which then sends a metal plunger rocketing out of the coil and into the housing of the pinball table, creating a distinct noise.

What Are the Origins of the Pinball Knocker?

While the exact history of the pinball knocker, and indeed the history of pinball in general, is patchy at best, some things are pretty certain.

During pinball’s formative years in the early ’30s, pinball found itself inextricably associated with gambling and organized crime. This being the case, many details of the iconic pastime have been lost to the decades, as well as a strict code of silence among those involved in their manufacturing.

Unfortunately for the law-abiding arcade attendees of today, pinball manufacturers of the mid-twentieth century thought it best not to document the details of their “crimes.” Due to their frequent use as gambling devices, pinball was banned in the United States beginning in the early ’40s and lasting until 1976 when the ban was finally lifted.

However, we do know that posters dating back as early as the 1940s are shown to have pinball machines advertised with knockers. While its origins may never be truly verified, it can be assumed that pinball knockers have been a part of the machines since their inception.

Why Does a Pinball Knocker Make Such A Loud Noise?

While pinball machines aren’t exactly known for being quiet, one particular sound seems to stand out amongst all the others emanating from the tables. For those skilled enough to achieve it, winning a free game will instantly activate the knocker and send that iconic thwack echoing throughout the room. But why exactly is the knocker so shockingly loud?

Although the exact reason for its existence is still a topic of discussion among historians and enthusiasts, the pinball knocker and its associated loud cracking noise are thought to function on a number of practical levels. The most commonly agreed upon reason for the knocker’s sound is simply a matter of marketing. If other customers in the arcade can hear that a player has won a free game, there is instant attention drawn to the table, potentially attracting more players.

The second, and probably most obvious reason for the knocker’s loud sound can be attributed to it being a simple and effective way to alert the player of their win. Making sure that the player knows they have won a free game is a crucial way of keeping them engrossed in the game, making it more likely that they will continue to sink quarters into the machine.

Why Don’t Modern Pinball Tables Have Real Knockers?

To the enthusiast community, the replacement of the traditional solenoid-fired physical knocker with that of a digital sound is a crime against gaming. Unfortunately, in the eyes of the manufacturers, it is simply not worth the money and effort to install real knockers in modern pinball tables.

Since all of the audio on newly built pinball machines is controlled digitally, it only makes sense for the knocker to be as well.

However, a digital knocker does come with the added benefit of volume control. But for those who simply cannot go without, there is a solution. Thankfully, there are still quite a few newer tables made by Stern that still have all of the appropriate connections and features to install the real deal.

Whether you are a collector in search of a replacement knocker, or you are the owner of a new table looking to retrofit a knocker into it, then you will be happy to hear that there are a number of places that still make and sell knockers.

For those looking to buy new, Pinball Life and MarcoSpecialties are well-known sellers of pinball replacement parts and accessories. For those looking to restore an old table, eBay is where you will find a sea of both Bally and Williams brand knockers for sale.


Since its mainstream adoption, pinball has become an icon of the arcade. It’s truly an experience of the senses, from the blinking lights, the frenetic flippers, the ball rolling at full speed, the music and the unmistakable “thwack” of the knocker.

While you may not find many arcades around anymore, the game lives on in restaurants and pizza places throughout the United States, continuing its legacy of joy in new forms.