According to examples, an apparatus may include a pump generator having a first resistance level and being positioned within a fluid circulation channel and a drop generator having a second resistance level and being positioned within a fluid ejection chamber. The apparatus may also include a control line connected to both the pump generator and the drop generator and a controller. The controller may output, at a first time, a first signal having a first pulse duration to the control line, the first signal to cause fluid in the fluid circulation channel to reach or exceed a first temperature and fluid in the fluid ejection chamber to remain below the first temperature and may output, at a second time, a second signal having a second pulse duration, the second signal to cause fluid in the fluid circulation channel and the fluid ejection chamber to reach or exceed the first temperature.