built-in EPROM reader for playing a single drum sound sample, and the all-analog SDS-200 (2 tom system), SDS-400 (4 tom system), and SDS-800 (bass, snare, and 2 tom system). These products were aimed at acoustic drummers who wanted to add a couple of Simmons pads to their kit on a budget. Some of these products also feature the run generator, which allows drummers to play a descending drum roll with a single pad hit. In 1985, Simmons introduced the SDS-9, a hybrid digital/analog brain with three changeable EEPROM channels (kick, snare, and rim) and analog-synthesized toms. It also featured 40 presets (20 factory and 20 user-programmable) and a built-in digital delay. This kit was yet another well received product for Simmons as it combines realistic sounds in an inexpensive, compact brain. Following customer feedback, Simmons also produced a new series of drum pads using "floating" drum heads and changeable shells. The snare drum had an extra trigger for the rim. Again, this improved the playability of the kit. Another brain was introduced in 1986 called the SDS-1000, and was, in effect, the same sounds as the SDS-9 (without the ability to change the EPROMS) in a slim 1U, MIDI-enabled, rack mountable unit. The snare sounds, however, are more realistic and clear than the SDS-9. The SDS-1000 also includes a "second skin" feature, which simulates the sound of dual-headed drums. The SDX In 1987, after the SDS-9, Simmons decided to enter into the high-end professional market and created the revolutionary SDX. It introduced new features that were unheard of in other electronic drums such as "zone intelligence" and "pad layering". Some of these ideas were not revisited by other companies until nearly 15 years after the SDX. Zone Intelligence allows for up to three samples to be assigned to different positional locations on a pad for a more realistic sound. With pad layering, up to nine different samples can be triggered via different strike velocities and positions, selecting samples from a 3 by 3 matrix. The samples can also be further manipulated by applying positive or negative values on a matrix (routed to both position and dynamic), simultaneously affecting the following aspects of the sound: volume, pitch, brightness, panning, noise element, and sample start point. All or any of these aspects of the sound, are both programmable and continuously variable dependent upon strike position and strike velocity and were user programmable