Process Displays
Hand/Off/Auto Switch
100 900 Control Station User Guide Revision 9
May 2014
Hand/Off/Auto Switch
The Hand – Off – Auto (HOA) switch permits state change requests. The block states are: Hand (manual
operation from an operator interface), Auto (default – requests are operated automatically), or Off (relay to
be switched to Bypass, Hand, or Auto), or Bypass (external manual operation of a device).
The HOA switch is also used with the Device Control function block to comprise a Pump Control
algorithm which is used to manipulate the state of a controlled device (pump).
Item Description
Feedback state State of the feedback signal. If connected to a Device Control block, this
shows the status of the device. See Table 31 Device states on page 99.
When the HOA block is used in conjunction with a Device Control block,
the feedback is typically referenced to the (STI) status output pin of the
Device Control block.
Current state indicator The rotary dial and yellow button indicate the selected state (Hand, Off,
Auto. Use buttons to change state. If the current state is BYPASS, any
requests to change the state are ignored.
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