This configuration is for use when the Commercial Fax will function as Either a Non-Secure Fax or a Secure Fax but not both without an operator actuating the A/B Switch. Use this for "Nite-Mode" operation when you want to receive unclassified faxes automatically when you are away.

For an Automatic Single-Line configuration see the Model 910 on the Accessory page.

A/B Switch Operation:
A: Unclassified Fax Mode - With the switch in the "A" position, incoming calls will ring the fax. The Secure Telephone is disconnected and will not get dial-tone.
B: Secure Fax Mode - With the switch in the "B" position, incoming calls will ring the Secure Telephone. The fax is disconnected and will not get dial-tone.

90si Setup:
Place the 90si in "2 Tel Line" and "Dual Mode On." with switch # 6 to the left and Switch #7 to the right...as shown in the switch diagram to the right of the drawing below.

Radio Shack stocks and sells a modular A/B Switch Box that can be used to implement this configuration. You will find its' details here. (External Link)