ZOLL PD 2000 - Page 80

FUNCTIONAL DESCRIPTION
To display an ECG trace, there are three intensity controls implemented.
The proper baseline intensity is selected with the intensity bit (INTFY).
When vertical deflection is fast, the beam speed on the phosphor causes
the trace to appear dim so an analog high slew signal proportional to
beam speed is used to increase the beam intensity, resulting in a uniform
ECG trace display. To indicate an R-wave detection by the CPU, an
additional intensity bit (SLEW) is used to substantially increase the beam
intensity. This results in a very bright segment of trace where the R-wave
was detected.
To display characters only BENBO is used to control the adjustable
current source and INT_2 is turned on to prevent the analog beam slew
detector circuit from having an effect.
1V-21