So I decided to look up some of their patents, they are quite interesting to read, complete schematic diagrams and a description of the various control algorithms and flowcharts..
The patents are from 1997-1998 or so and relate to :
(1) using a single 2 wire DC loop for both DC power and signaling control of both audio and visual indicators, instead of the previously needed 2 wires for audio and 2 wires for visual (i.e. prior to their design and patent, 2 pairs (4 wires) were needed, using simple signalling where power is either applied or not. Applying DC power on the audio pair would enable the audio alarm, and applying DC power on the visual pair would enable the visual signal. Turn it off to silence the alarms)
(2) their 2 wire method uses short 100ms power drop-outs every second (i.e. on/off pulses) of the DC power signal to synchronize multiple chained alarm units in a building so they flash in unison and "whoop-whoop-whoop" up and down in unison throughout a building
(3) using similar voltage drop-out sequences at specific positions in time to turn off the audio, or turn of the visual, or both, from a central control panel
(4) an interface box and method of converting the old style 4-wire signaling to their 2-wire DC power and signalling control loop, to allow these alarm units to be retro-fitted into older installations
(5) a method of measuring inductor current in a DC-to-DC converter using an opto-coupler, to provide adequate charge on the strobe capacitor, in order to maintain UL mandated brightness of the strobe even in the event of DC power dropping to 80% of it's nominal value during an alarm
(6) a universal mounting backplate that fits single outlet boxes, dual outlet boxes, round boxes, square boxes and international 100mm boxes, thereby permitting an installer to inventory only one type of mounting backplate
(7) a method of preventing the installer from installing the unit upside down or right to left (instead of left to right) when using said universal mounting bracket. This is to make sure the unit is installed correctly to emit most of its light in the downward direction to meet UL visibility specifications.
This is not all of them. There were a few patents that I didn't look into.