Abstract: Recording or measuring equipment is provided with a spring clamp or clip for holding a replaceable writing unit by the ink reservoir of the writing unit. The reservoir carries a pen with a fiber or laminar tip and has a vent at or near the end shaped for insertion in the clamp or clip. A plug equipped with a gripping knob is inserted in the vent and the vent is so located that when the plug is so inserted, the ink reservoir cannot be inserted into and held by the clamp or clip, thus assuring that the vent is opened before the pen goes into use.

Abstract: The disposable printing head assembly includes a printing head frame structure fitted with a plurality of printing tips or pens. The printing head frame structure includes a plurality of separate store chambers including store material for containing the color printing material. The color store material may be the same or of different colors from one chamber to the other. At least one printing tip is disposed in each color store chamber. The printing tips are formed with different printing symbols such as a point, cross, star or circle.