Commentary about the Ampico On-Off, or Automatic switch (revised March 24, 2025) by John A Tuttle. There are two components that control the operation of the Automatic Expression Cut Out Block. They are the Ampico On-Off switch and the Automatic Cut-Out Block. In most cases, the Automatic Cut-Out Block utilizes a poppet type valve. Therefore, when the pouch is activated by atmosphere, vacuum to the Automatic Expression Cut Out Block is turned Off, which in turn allows the pouches in that block to inflate and prevent signals from the trackerbar from reaching the Bass and Treble Expression devices. It also allows atmosphere to enter the Cancel pneumatic to prevent the chance of any of the intensity valves being locked 'open'. Some (maybe most) units did use a poppet type valve. So, the Hole in the switch is 'Open' to the atmosphere when the switch is in the 'Off' position (as per Brian Grado) so that vacuum is applied to the Automatic Expression Cut Out Block which allows signals from the trackerbar to flow unimpeded to the expression devices. With the vacuum 'off' to the Automatic Expression Cut Out Block, the pouches relax and vacuum from the bleeds in the expression devices inflate the pouches which in turn seals the orifices leading to the expression devices, which in turn prevents signals from the trackerbar from getting to the expression devices. Either way you look at it, when vacuum is applied to the Automatic Expression Cut Out Block, it sucks the pouches inwards (or down into the pouch well), which in turn allows signals to flow from the trackerbar to the expression devices. That being the case, when making the switch it's important to know if the Automatic Expression Valve block is a poppet type of standard valve type. For more information, see graphic Automatic-Expression-Cut-Out-Block.jpg under Ampico-A\Brass Switches\Automatic -Ampico 'On'-'Off' Switch The Automatic Cut-Out Block uses a regular type valve, not a poppet type valve. Therefore, vacuum is present at the output only when the block is in the 'ON' mode. This means that the switch must provide a path to atmosphere when it is in the 'ON' position. When the switch is in the 'ON' position, atmosphere flows through the switch. This allows vacuum to enter the Automatic Expression Cut Out Block which in turn allows expression signals to pass through to the expression devices. In the 'OFF' position, atmosphere is cut off. Article posted in the Mechanical Music Digest on June 10, 2024 Ampico 'A' Automatic Cut-Out Valve Block and Automatic On/Off Switch Regarding the Automatic Cut-Out Valve Block and the associated Automatic On-Off switch (sometimes called the Ampico On-Off switch), I'm trying to find out if all Ampico 'A' systems used a Primary-Type valve (poppet-type) or a regular-type valve in the valve block. I ask because the switches that I sell for the On-Off function were designed to allow atmosphere to trigger the valve (in the Automatic Cut-Out Block), which in turn applies vacuum to the Expression Cut-Out Block, when the On-Off switch is in the 'On' position. However, if the valve in the Automatic Cut-Out Valve Block is a Primary-Type valve, an atmosphere trigger would turn the vacuum to the Expression Cut-Out Block 'Off'. You can see that would be a 'problem'... When I had the base and cap for the switch manufactured, I copied the design of switches made by Bob Streicher, Don Teach, and PPCo. However, I recently had a customer complain that, in their Ampico 'A', the switch turns the expression 'Off' when the switch is in the 'On' position, which would indicate that the valve in the Automatic Cut-Out Valve Block is a Primary-Type valve. Also, I've discovered that some of the earlier systems (like the Stoddard in upright pianos) didn't have an Automatic Cut-Out Valve Block. Instead, the supply vacuum for the Expression Cut-Out Block is turned 'On' and 'Off' directly by the switch itself. Any information you can provide about the conundrum will be appreciated. Musically, John A Tuttle Brick, NJ, USA Player-Care.com