Intermec Janus 2020 User Manual page 541

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Glossary
PC Standard communications protocol
A communications protocol that handles data transfer on a character-by-
character basis or by either filling a receive buffer or transmitting a buffer of
data. This protocol is designed to be compatible with the standard PC BIOS
functions. The one exception is that the PC Standard protocol can buffer data
that is received to avoid losing characters if a program has not checked for data
recently.
physical RAM drive
See RAM drive.
Plessey Code
A fixed length, continuous, and not self-checking bar code symbology. Plessey
code is pulse-width modulated. It includes a start character, data characters, an
eight-bit cyclic check digit, a termination bar, and usually a reverse start
character.
Point-to-Point protocol
Point-to-Point is an unsolicited protocol in which the reader transmits data
whenever it has something to transmit. The data is followed by a CR LF as the
EOM characters. The reader is always in a receiving state and does not wait for
select commands. This protocol does not perform any error checking or
acknowledgment handshaking. Point-to-Point protocol is typically used to
connect the reader to a CRT terminal or host computer.
POL
Poll character. Sent by the host to request reader data. For User-Defined
Multi-Drop protocol, you must define a unique character for each reader on a
data line.
Polling Mode D
Polling Mode D is a communications protocol that requires the host computer
to ask the reader for data it might have (polling) and to request to send data to
the reader (selecting). Polling Mode D is used to connect multiple devices to a
single multiport controller. PC-IRL uses this protocol.
POST
Power-on self test. This test runs when you warm or cold boot the reader. The
test ensures that the reader's hardware and peripherals are operational.
postamble
A field of data that is sent after the data in a message. It is typically used to tag
transactions from the bar code reader for rapid processing by the host, and it
expands the data field (record) length. Similar to the preamble.
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