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inside the selection frame of the symbol. When the crossed arrows are visible, click

on the symbol and keep the mouse button pressed. After about 1 or 2 seconds the

cursor will briefly blink and change to the drag symbol. Drag the object into the

Gallery and release the mouse button. When you move the mouse into the Gallery

field, the cursor shape changes once more (see Figure 221).

Figure 221: Crossed arrows > Drag symbol > Gallery

symbol

Tip

Zoom in on very small graphics before you try to move them so that the

crossed arrow symbol can be clearly seen.

When you have placed all the symbols in the Gallery they can be titled. Right-click on

a symbol, choose Title from the menu and type the symbol name (AND, OR).

The symbol library is available to all OOo modules, for all users who have the

permission/rights to access it. Making the drawing collection available as a Draw file

is the simplest way to distribute a symbol library to other users. After opening the

drawing, other users can easily transfer the drawing objects into their own Gallery, as

described above.

Drawing a logic circuit diagram using the Gallery

The use of the symbol library which you have created and placed in the Gallery can

be illustrated by using the blocks to draw a half adder (see

http://en.wikipedia.org/wiki/Half_adder#Half_adder). You can precisely place all the

drawing objects with the help of Draw’s snap functions. The following instructions

are only one way to achieve this objective.

Begin with a new drawing. Set the unit of measurement to centimeter, a grid point

spacing of 0.5 cm and subdivision of 4 points. Activate the grid, guiding lines, and

associated snap functions.

In the first part of the exercise you should draw only the two signal leads a and b, the

two INVERTER gates and the two AND gates.

Begin by drawing the two signal leads. To make it a bit easier, you can use the values

in the following table.

Start point Length

Signal wire a X = 2 cm / Y = 3.0 cm 5.5 cm

Signal wire b X = 3 cm / Y = 3.0 cm 5.5 cm

After drawing the two signal leads, you begin the hardest part. With grouped objects

the snap function works only on points on the outside contours. The only way to work

with these blocks as a unit, however, is as a grouped object. The input and output

leads must lie precisely on grid points if the connecting lines are to be exactly

horizontal or vertical.

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