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Fast Select is an optional user facility that can be set on a per-call basis. This facility allows the exchange of user data while the virtual call is being established. Usually, the user must initiate a call and get a connection established message before sending data. With Fast Select, the user can include data in the initial Call Request packet.
NOTE: The user can include data in the Call Request packet without using Fast Select. Without Fast Select, the user can put up to 16 bytes in the Call Request packet.
When Fast Select is indicated in a Call Request packet, the packet can contain a Call User Data field of up to 128 bytes. An additional field of up to 128 bytes of called or clear user data can also be included by the called DTE in the Call Accepted or Clear Request packet.
Two options are available with Fast Select:
Fast Select makes the data field more useful for short-duration, low-volume, transaction-oriented applications. This facility often is used in the environment of retail point-of-sale and credit card authorization terminals.
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