A continuous liquid ejection system comprising: a liquid chamber in fluidic communication with a nozzle, the liquid chamber containing liquid under pressure sufficient to eject a liquid jet through the nozzle; a drop formation device (42; 55) associated with the liquid jet, the drop formation device (42; 55) being operable to produce a modulation in the liquid jet to cause portions of the liquid jet to break off into a series of drop pairs traveling along a path, each drop pair separated in time on average by a drop pair period, each drop pair including a first drop and a second drop; a charging device including: a charge electrode (44; 45) associated with the liquid jet; and a source of varying electrical potential between the charge electrode (44; 45) and the liquid jet, the source of varying electrical potential providing a waveform, the waveform including a period that is equal to the drop pair period, the waveform including a first distinct voltage state and a second distinct voltage state, the charging device being synchronized with the drop formation device (42; 55) to produce a first charge state on the first drop and to produce a second charge state on the second drop; a drop velocity modulation device (41; 54) that varies a relative velocity of a first drop and a second drop of a selected drop pair to control whether the first drop and the second drop of the selected drop pair combine with each other to form a combined drop, the combined drop having a third charge state; and a deflection device that causes the first drop having the first charge state to travel along a first path and causes the second drop having the second charge state to travel along a second path, and causes the combined drop having the third charge state to travel along a third path; characterized by, the source of varying electrical potential between the charge electrode (44; 45) and the liquid jet being not responsive to print data supplied by a stimulation controller, and characterised in that the drop velocity modulation device (41; 54) further comprising: a drop velocity modulation transducer associated with one of the liquid chamber, the nozzle, and the liquid jet; and a waveform source that supplies a drop velocity modulation waveform to the drop velocity modulation transducer (41; 54), wherein the drop velocity modulation waveform supplied to the drop velocity modulation transducer (41; 54) is responsive to print data supplied by a stimulation controller. a liquid chamber in fluidic communication with a nozzle, the liquid chamber containing liquid under pressure sufficient to eject a liquid jet through the nozzle; a drop formation device (42; 55) associated with the liquid jet, the drop formation device (42; 55) being operable to produce a modulation in the liquid jet to cause portions of the liquid jet to break off into a series of drop pairs traveling along a path, each drop pair separated in time on average by a drop pair period, each drop pair including a first drop and a second drop; a charging device including: a charge electrode (44; 45) associated with the liquid jet; and a source of varying electrical potential between the charge electrode (44; 45) and the liquid jet, the source of varying electrical potential providing a waveform, the waveform including a period that is equal to the drop pair period, the waveform including a first distinct voltage state and a second distinct voltage state, the charging device being synchronized with the drop formation device (42; 55) to produce a first charge state on the first drop and to produce a second charge state on the second drop; a charge electrode (44; 45) associated with the liquid jet; and a source of varying electrical potential between the charge electrode (44; 45) and the liquid jet, the source of varying electrical potential providing a waveform, the waveform including a period that is equal to the drop pair period, the waveform including a first distinct voltage state and a second distinct voltage state, the charging device being synchronized with the drop formation device (42; 55) to produce a first charge state on the first drop and to produce a second charge state on the second drop; a drop velocity modulation device (41; 54) that varies a relative velocity of a first drop and a second drop of a selected drop pair to control whether the first drop and the second drop of the selected drop pair combine with each other to form a combined drop, the combined drop having a third charge state; and a deflection device that causes the first drop having the first charge state to travel along a first path and causes the second drop having the second charge state to travel along a second path, and causes the combined drop having the third charge state to travel along a third path; a drop velocity modulation transducer associated with one of the liquid chamber, the nozzle, and the liquid jet; and a waveform source that supplies a drop velocity modulation waveform to the drop velocity modulation transducer (41; 54), wherein the drop velocity modulation waveform supplied to the drop velocity modulation transducer (41; 54) is responsive to print data supplied by a stimulation controller.