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Rapicom 450 facsimile file format (RFC0769)

IP.com Disclosure Number: IPCOM000003817D
Original Publication Date: 1980-Sep-26
Included in the Prior Art Database: 2000-Sep-13
Document File: 2 page(s) / 4K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Postel: AUTHOR

Abstract

Introduction:

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 75% of the total text.

Network Working Group J. Postel

Request for Comments: 769 ISI

26 September 1980

Rapicom 450 Facsimile File Format

---------------------------------

Introduction:

Several organizations in the ARPA Internet community have RAPICOM 450

facsimile machines interfaced to computers. This allows these

organizations to enter a facsimile representation of a page into a

computer file, and to produce a page from stored facsimile data. These

organizations can exchange stored facsimile data via file transfer and

other protocols. The purpose of this note is to document the format

used for these files so that other organizations with compatible

facsimile devices can join in this information exchange procedure.

The Rapicom 450:

The Rapicom 450 has a built in encoding/decoding scheme. It produces

data blocks of 585 bits. There are "set up" blocks and "data" blocks.

The machine sends/receives several copies of the set up block, but since

they are identical only one set up block is stored in the file.

Records:

Each 585 bit block is placed in a record of 8-bit bytes. The record

format is a length byte, a command byte and the data bytes. Each record

is an integral number of bytes. The length value includes the length

byte and the command byte. The command describes the data in the data

field.

0 1 2 3 length

+--------+--------+--------+--------+---//---+--------+--------+

| length | command| data |

+--------+--------+--------+--------+---//---+--------+--------+

Rapicom 450 Facsimile Record

Commands:

56 - SET-UP

The command code 56 (70 octal) indicates the following data field is a

set up block.

26 September 1980

Rapicom 450 Facsimile File Format RFC 769

57 - DATA

The command code 57 (71 octal) indicates the following data field is a

data block.

58 - END

The command code 58 (72 octal) indicates that this is the last record

in the file. In this case the length may be 2, indicating that there

is no data in this record.

Conventions:

In the files exchanged to date, each record contains one block. This

means the data field is 74 bytes long (585/8=73.125), and the length

field has the value 76 (114 octal), except the last record which may

carry no data and have a length of 2.

The first record of a file is always a SET UP record, the following

records are DATA records, until the last record which is an END record.

Details:

The 585 bit data block is encoded by the Rapicom 450 and so can not be

used a bit map unless the encoding/decoding procedure is known and used.

The first 24 bits of the block is always a synchronization mark with the

value 271 141 344 in ...