Security section needs user interaction guidelines

[marcoscaceres]

It would be good if the sec/priv section described some user interaction guidelines... like not exposing A-D buttons to the user - and perhaps some other things.

[marcoscaceres]

assigning to @jplyle. Be great to have this for the next F2F.

[marcoscaceres]

Wikipedia states that:

Present-day uses of the A, B, C and D keys on telephone networks are few, and exclusive to network control. For example, the A key is used on some networks to cycle through different carriers at will (thereby listening in on calls). Their use is probably prohibited by most carriers. The A, B, C and D tones are used in radio phone patch and repeater operations to allow, among other uses, control of the repeater while connected to an active phone line.

There is probably scope in the UI guidelines for the exclusion of A, B, C and D.

[marcoscaceres]

Having said that, there may be some private telephony networks that make use of A-D...