# Introduction ### About This Document This document describes how to communicate with Secure Card Reader Authenticator (SCRA) devices which implement MagTek Messaging Schema (MMS) and the DynaFlex II Go system architecture. The document uses bold face to: * Highlight terms / concepts being formally defined in the current sentence / paragraph * Highlight important distinguishing keywords in sentences * Indicate hyperlinks to other sections / tables The document uses a small number of annotation standards that are important to understand: * Hexadecimal values are prefixed with 0x unless the context clearly indicates an un-prefixed number is hexadecimal (for example, TLV tags, lengths, and values are always assumed to be hex). * Binary values are prefixed with 0b unless the context clearly indicates the value is binary. * Decimal values are not prefixed unless required for clarity, in which case the prefix is 0d. The standard documented by this document makes extensive use of Tag-Length-Value encoding. Section Tag-Length-Value (TLV) Encoding describes how to encode and decode TLV, and how to read the tables in this document that describe TLV data objects. --- # 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://developer.magtek.com/hardware/card-readers/mms-dyna-devices/emv-common-kernel/dynaflex-ii-go/documents/programmers-manuals/programmers-manuals-commands/introduction.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.