of which allows chaining of up to 128 bars of patterns. A small battery retains memory content when the DR-110 was switched off. Interfacing A "V-trig" clock pulse (+6V, 10ms duration) can be used, via a 3.5mm mini-jack, to allow other "slave" synthesizer units (e.g. arpeggiators) to synchronize to the DR-110 accent section. The DR-110 has a 10kΩ impedance unbalanced mono audio output, available on a ¼" phone connector socket. This output can be plugged into a keyboard amplifier or PA system. The socket is also configured as the "Roland P-bus," which meant it can be used as a simultaneous audio input, the input source being mixed with the output signal. A separate 3.5mm headphone output socket is also present. The DR-110 does not offer any kind of external "sync", but can be fitted with third-party DIN-sync interfaces available from other companies. Internally, the DR110 runs at 12ppqn (pulses per quarter note), so extra circuitry is needed to interface it with the Roland DIN-sync standard of 24ppqn. To access the Test Mode function, users press and hold both the Start and Stop buttons when turning on the unit. The entire LED screen shows. The user presses the blue buttons one at the time, a big "OK" appears in the programming grid after last button. The user turns the unit off and then on to exit test mode and go back to normal mode. References Boss Dr. Rhythm DR-110 Owner's Manual (Nov.1983) Boss DR-110 Service Notes (First edition, Feb.1984) Notes Drum machines Musical instruments invented in the 1980s Boss Corporation