# EMR ## Overview EMR technology was introduced to drawing tablets by Wacom. And they held all the core key patents to EMR. Those core patents have expired and now other manufacturers can build increasingly sophisticated EMR designs which are begin to rival Wacom products. ## EMR key features * Powering the pen - With **Passive EMR** the pen gets power from proximity to the tablet. However with **Active EMR**: The pen gets power from a battery inside. More here: [Active EMR vs Passive EMR](/drawtab/tech/emr/active-emr-vs-passive-emr.md) * Position detection - The basics of how the tablet detects position are described here: [EMR position detection](/drawtab/tech/emr/emr-position-detection.md). * Hover (i.e. proximity detection) - * Pressure detection - See this document for details on [EMR pressure detection](/drawtab/tech/emr/emr-pressure-detection.md). It also contains a clarification of pressure detection in the video below (which depicts a very old way of doing pressure detection). * Tilt detection - more here: [EMR tilt detection](/drawtab/tech/emr/emr-tilt-detection.md) * Barrel rotation detection - very rare in EMR pens * Communication of button press information ## Explanation of how EMR works NOTE: This video's explanation of how pressure works describes a very early EMR pen design that involves physically moving the ferrite core inside the inductor coil and thus inducing a change in the resonant frequency of the pen's signal. Modern EMR pens have a design where the ferrite rode is stationary relative to the inductor coil and pressure is digitally encoded in the signal coming from the pen. {% embed url="" %} ## Deeper EMR Technical resources If you want to go really deep into how EMR works, go here: [EMR](#emr-technical-resources) ## Notes on EMR ### EMR Concepts vs Implementation Think of the EMR design illustrated in the video as a baseline example that demonstrates the fundamental concepts, different manufacturers can tweak this design in their implementation. ### **Resonant frequency** The exact resonant frequency used by the pen will vary. In the case of the Wacom Bamboo Fun tablet (CTH-661) the frequency is around 750KHz. Source: the last 10 seconds of this scanlime video: ### **How fast does the tablet switch between sensing the pen and sending it power?** We don't know. We suspect this is MUCH faster than a typical pen report rate of 200Hz. ## **Other digital pen technologies** Even though EMR is used in drawing tablets, there are many other pen technologies in the market, such as AES, Apple Pencil, etc. More here: [Digital pen tech](/drawtab/tech/digital-pen-tech.md) ### Apple Pencil The Apple Pencil does not use EMR. Apple uses a proprietary protocol for their pen. If you are curious about what is inside an Apple pencil, see this video: --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.sevenpens.com/drawtab/tech/emr.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.