RI
Ring indicate signal. RI alerts a modem to a call
waiting on the attached telephone line.
ROM
Read-only memory. In a PTC, ROM chips contain the
operating system and the application program.
RS-232
An Electronic Industries Association (EIA) standard
that defines the connector, connector pins, and signals
used to transfer data serially from one device to
another.
RTS
Request-to-send signal. RTS initiates the data
transmission sequence on a communication line
between a modem and a terminal device.
RXD
Receive data signal. RXD indicates that a device is
currently receiving data.
signals
Electronic impulses that transmit data from one
device to another.
software
A stored program or set of programs that is loaded
into RAM for execution. Contrast with
spread
spectrum
A radio communication technology that distributes an
RF signal over a wide range of frequencies for
transmission; it then “despreads” the signal to the
original frequency range at the receiver.
TCAL
Telxon Common Application Language. Telxon’s
proprietary programming language for PTCs.
two-way
communication
Exchange of information between two devices. After
each block of data, the receiving device sends a
positive or negative acknowledgment to the sending
device.
TXD
Transmit data signal. TXD indicates that a device is
currently transmitting data.
VDC
Volts direct current. A unit of measure of electric
potential or potential difference in a unidirectional
current.
54
