Toshiba VF-S15 Instruction Manual page 229

The override functions calculate output frequency by the following expression:
Frequency command value × (1+
1) Additive override
In this mode, an externally input override frequency is added to operation frequency command.
[Ex.1: VIA (Reference frequency), VIC (Override input)] [Ex.2: VIB (Reference frequency), VIA (Override input)]
Output frequency

Override
(VIC input)
Ex.1:
f660 = 3 (VIC input), f661 = 0 (disabled)
Output frequency = Reference frequency + Override (VIC input [Hz])
Ex.2:
f660 = 1 (VIA input), f661 = 0 (disabled)
Output frequency = Reference frequency + Override (VIA input [Hz])
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Value [%] selected with 
Over-ridden frequency
(
0
10V
)+Value [Hz] selected with f660
100
Output frequency
Forward run
Override
VIA input
)
(VI/II input)
(Reference
frequency)
-10V
F-117
Over-ridden frequency

(
0
10V
Reverse run

E6581611
VIB input )
(Reference
6
frequency)