Check for resistance between terminals in each switch position.
Switch
Connector terminal
Resistance
(±5%)
Output voltage
(± 0.22)
Voice
2-4
10.71 kΩ
3.5 V ± 0.22
Call off
18.91 kΩ
4.0 V ± 0.22
Call
40.91 kΩ
4.5 V ± 0.22