Background

Sonim develops push-to-talk (PTT) software for carriers, handset manufacturers, and infrastructure vendors. As part of its product differentiation strategy, Sonim wanted to be able to provide a detailed PTT client specification to its partners.

The project

Sonim doesn’t write client applications—it provides API’s and technology to allow partners to write their own clients. I developed a universal HI client specification that could be applied, with minimal changes, to a wide variety of handsets ranging from inexpensive, small-screen devices to full-featured smartphones.

Users learn to operate handsets via muscle memory and I couldn't assume the user would be looking at the screen at all times. Therefore, in order to define a complete user experience I had to provide detailed specs to show how pressing handset hard buttons would control the PTT client at every step in every process.

The primary PTT client design specification detailed how the PTT client would work on an average handset equipped with a dedicated PTT button.

A chart running underneath the screen shots described what should happen if the user pressed certain keys on the handset.

One variation on the “universal” design was for a handset with a very small screen and no onscreen softkeys.

The smartphone variation could take advantage of things like menus and dialog boxes.