7.6 Design Guidelines 247 taps hot (at high volume levels) so that you can hear quiet inputs well, without the worry that when something loud (like a DTMF key press) comes along your ears will get blasted. The Alesis 3630 compressor/limiter is a workhorse in our lab that can often be sourced for as low as $100. 7.6 DESIGN GUIDELINES IVR system interfaces need to be inherently easy to use. This section is intended to give IVR developers a set of tools that they can use during the design stage to help ensure that their product meets functional and usability expectations for a broad range of users. It should be noted that no set of rules or guidelines alone will lead to the development of an optimally usable and useful IVR. The goal in any interface design effort is to find the best "fit" between a system's specific require- ments and the consistency and usability benefits that will result from the applica- tion of design guidelines. To achieve this goal, it is recommended that guidelines be used as part of a broader process, including usability testing. 7.6.1 General IVR Design Information