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Installation and Operations Guide

VLX/ACM-VLX/EXP/AXM operation and maintenance

Using H-O-A switches and trimpots

For each AO and BO terminal on an EXP/AXM, a Hand-Off-Auto (H-O-A)

switch enables manual override of the commanded output status. For AOs, the

H-O-A switch is combined with a trimpot, which drives the output when the

corresponding H-O-A switch is in the H position.

H-O-A switches always override all software commands and backup mode

values.

H-O-A switch status and trimpot values are reported through reserved AVs in the

VLX/ACM-VLX for use in software. See “Appendix G: H-O-A and trimpot

status values” on page 95.

Figure 27 Status LED flas h patte rns in the e vent of EXP/AXM communication dis ruption

Table 16 H-O-A s witch ope ration

Switc h pos itio n BO o pe ratio n AO o pe ratio n

A (de fault) Software controlle d Software controlle d

O OFF Off (0%). One-second de lay be twee n

switch s e t and output re s pons e to

accommodate trans itions from H to A

through this position.

H ON Trimpot control. Lift the cover and us e a

small scre wdrive r to adjus t the trimpot

corres ponding to the output. Fully

counte r-clockwise = 0% (0 mA or 0

VDC), Fully clockwis e = 100% (20mA or

10 VDC).

Honeywell ALERTON ACM-AXM User Manual

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