Specifications

Appendix C - Glossary of Terms RS-422 And RS-485 Applications Ebook
Page 107 of 137 Manual Documentation Number: <DocNumber>
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E
Earth Ground
A ground that directly connects to the earth though grounding stakes and
buried copper wire or metal water pipes buried in the earth. Usually some form
of earth ground is provided at the entry point of phone lines or AC power. The
power ground within a building can vary from earth ground, and earth grounds
at different locations can have voltage differences between them, especially
during electrical storms.
Echo Off
In a half duplex two-wire RS-485 system, the receiver is normally disabled
during transmit, so the data is not echoed back to the receiver even though
the receiver inputs are connected to the transmitter outputs. An Echo Off
switch or jumper (if provided) can set the receiver mode so that transmitted
data is not fed back to the receiver. It sets the receiver for two-wire RS-485
mode.
A communications terminal program may depend on the remote terminal to
echo the characters typed locally. If the program displays the typed
characters, and they are echoed by the remote device, each character is
repeated. The Echo off setting turns off local echo so only the returned
characters are displayed. The reverse case is that the remote terminal does
not return typed characters, and the user cannot see what he/she is typing.
Then echo must be set on locally.
Echo On
In a half duplex two-wire 485 system, the receiver is normally disabled
during transmit, so the data is not echoed back to the receiver even though
the receiver inputs are connected to the transmitter outputs. An Echo On
switch or jumper (if provided) can set the receiver mode so that it is
enabled all the time, and transmitted data is returned to the receiver. Echo
on can be used in two-wire mode, but since the setting enables the receiver
all the time, this setting is typically used in four-wire RS-485 and RS-422
modes.
A communications terminal program may depend on the remote terminal to
echo the characters typed locally. If the program does not receive the