Specifications

2–29
Principles of Operation
Print Mechanisms
Hammer Bank, Shuttle, and MPU
Printing is synchronized with shuttle movement by signals from the magnetic
pickup unit (MPU). The MPU, located next to the flywheel timing disk, is so
oriented that timing signals relate precisely to the shuttle position. (See
Figure 2–18.) Variations in magnetic reluctance are sensed by the MPU from
apertures on the timing disk as it rotates, generating SYNC pulses. Two
aperture locations at opposite ends of the disk are of double width (material
between two adjacent apertures is removed). These double width apertures
separate the 284 single width apertures into two groups and generate a
RESYNC signal coincident with the shuttle starting to move from left to
right.
One rotation of the disk provides four back–and–forth shuttle cycles, which
equals eight printing periods. Each printing period is followed by a
turnaround period when the shuttle movement is reversed, paper is advanced
a distance determined by the vertical dot density, and no printing occurs.
Typical signal levels received from the magnetic pickup are:
SYNC: 2.5 to 5.5 Vpp
RESYNC: 4 Vpp minimum
Operation of the hammer bank and shuttle is also described on page 2–4.