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ARQ-1000B |
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The ARQ1000B allows transmission and reception of radio
teleprinter signals with the added feature of error
correction. The ARQ1000B uses the ITU 7-unit code as defined
by CCIR Recommendations 476 and 625. This code is also known
by the commercial trade names of "TOR" and "SITOR." All
features of 476 and 625 are supported in the ARQ1000B
including "Mode A" (ARQ), "Mode B Collective Broadcast" (FEC/CB),
and "Mode-B Selective Broadcast" (SEL-FEC/SB). A "monitor"
mode is also available so that any of these modes may be
received and displayed without requiring transmission of the
normal "handshaking" receive station responses. Up to
9-digit selcals are automatically recognized and
accommodated. Free signal recognition and stop scan features
are standard. A by-pass mode is also included so that
standard Baudot or ASCII encoded signals may be passed
directly to the teleprinter without changing wires or using
external switches. The ARQ1000B can also be controlled
through the terminal keyboard by a series of simple
commands. A command menu screen is available to assist the
operator.
When used in the ARQ or "A" mode, the ARQ1000B communicates
with another station by exchanging bursts of information.
The station originating the message (Information Sending
Station or "ISS") sends groups of three characters per data
burst. The ARQ code is designed so that errors in reception
of any character are easily determined. The receiving
station (Information Receiving Station or "IRS") transmit a
one character "accept" or "reject" control character back to
the ISS to indicate correct or incorrect reception. If the
3-character block was received correctly, the ISS then
transmits the next 3-character block; if not, the original
block is repeated until it is correctly received. The
process continues with repeats as necessary until the
complete message has been passed. The direction of
communications may be reversed at any time with a control
signal so that error corrected text may be relayed in both
directions. All ARQ error corrected data uses synchronous
100 baud data as described by 476. The ARQ mode is only used
for two-station communications and must originate with
digital recognition of the receive station's call sign or
access code. This access code (SEL-CAL) is programmed from
the terminal keyboard and stored in non-volatile memory.
The FEC (collective broadcast) is used to transmit a message
to a number of receiving stations. A two-way accept/reject
system is not used in this mode. Rather, the transmitted
characters are sent twice, interleaved so that there is a
time delay between the two sets of data, providing time
diversity protection against reception of errors. The
receiving station FEC terminal digitally sorts the
interleaved codes, checks each letter for errors and passes
the correct text to the printer. The FEC mode uses 100 baud
synchronous data.
The SEL-FEC mode is used for selective broadcast of messages
only to stations whose selective-call code corresponds to
that transmitted. Data transmitted using SEL-FEC mode is
sent in the same format as that used for FEC mode except
that the polarity of the data pulses is inverted. The
selective call code is also keyboard programmable and stored
in non-volatile memory.
The monitor mode allows the station to receive and decode a
message whether it is sent using ARQ, FEC, or SEL-FEC mode.
In monitor mode, the ARQ1000B automatically switches to the
correct mode and prints received text. Reception of either
the ARQ access code or SEL-FEC selective call code is not
required. Since two-way error correction is not available in
ARQ monitor mode, re-synchronizing time delays are reduced
and the ARQ1000B quickly synchronizes to an ARQ
transmission. The monitor mode is an additional feature of
the ARQ1000B not formally defined by CCIR recommendations.
The ARQ1000B is a code conversion device and connects
between the FSK modem and terminal. A wide selection of I/O
interface options are available for connection to the modem
and terminal. Separate (full duplex) connections are
provided for the terminal's keyboard and printer.
Handshaking control signals are provided for interfacing
with the printer, keyboard, tape transmitter, or video
terminal. Either Baudot or ASCII terminals may be used at
data rates from 45 to 300 baud. Outputs are also provided
for indication of reception of the selective call code and
to control the transmit-receive line of the radio system.
When the ARQ1000B is turned off, modem data is connected
directly to the terminal.
The ARQ1000B is designed to interface HAL Communications
RTTY terminals such as the DS3486 and the ST8000. A total of
30 LED indicators and 11 front panel switches are provided
to give full control and status indications of ARQ1000B
operation. The ARQ access code, SELCAL code, WRU/HERE IS
response text are keyboard programmable and stored in
non-volatile memory. The ARQ1000B may be either rack mounted
or placed on the operating table (tilt bail included). The
ARQ1000B operates from 105-130/210-250 VAC 50/60 Hz power.
Options for the ARQ1000B include a built-in modem (M1700)
and a high voltage loop supply (LP1200A).
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Data Sheets:
ARQ-1000B
PDF
(40k) |
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