The Ace Tone FR-1 "Rhythm Ace" was Roland's very first preset drum machine. Circa 1967.
Before it came the The Rhythm Ace R-1 (1964) & R-3 (1966). No one knows if there was a R-2.
For the record, the R-1 was the world’s very first transistorized drum machine. It didn't have preset patterns. Nor did the R-3.
So in 1967, an automatic version, the Rhythm Ace FR-1,
followed and was adopted by the Hammond Organ Company. Ace Tone developed the preset rhythm-pattern generator using a diode matrix circuit.
The Diode Matrix used a pulse generator & frequency dividing counter. The
outputs were connected to a matrix of diodes which were arranged in AND and OR configurations. Logic circuits. :-)
The matrix output drove the various drum voices.
The diode matrix enabled the drum to have 16 preset patterns. You can cascade & mix these up by pressing two buttons simultaneously. The possible combination of rhythm patterns were more than a hundred.
In the USA, the FR-1 was sold under the "Multivox" brand. It the UK it was marketed as the "Bentley Rhythm Ace".
Also, the four round white buttons enable you to mute the cymbal, claves,
cowbell and bass-drum sounds.
For more info on the history of Roland Drum Machines click here