Siemens SIMATIC HMI TP 170A Equipment Manual page 104

Glossary
Tag
A defined memory location in which values can be read from and written to. This
can be performed from the PLC or via the operating unit. Depending on whether
the tag is linked to the PLC or not, a distinction is made between "global" tags
(process tags) and "local" tags.
Touch panel
This is an operating unit without a keyboard. The touch panel (abbreviated to TP)
is operated via the contact-sensitive screen elements.
Trend curve
Represents values from the PLC on the screen as a continuous line or bar.
TTY
Standard interface for serial data transfer at a defined current level. Transmitter
and receiver are electrically connected.
Glossary-8
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