Philips V24CT User's Reference Manual page 257

The calibration pulse varies according to the wave type:
ECG 1 mV square wave
RES 1 ohm M-shaped wave
All Pressures Stepped wave with 30, 60, 120, and 180 mmHg
increments
For pressure scales of 240 and 180, all four steps are displayed. At lower
ranges, however, not all the steps are displayed since one or more steps
exceeds the full scale range.
If you don't want to insert a calibration pulse or mark an event after
Note—
Mark Event
you have pressed
).
Main Screen
Viewing Patient Data
, press any other hardkey (such as
Trends and Calculations 8-19