Apple IIe - Page 18

18 Apple lie Users Handbook
It is unimportant what data values are actually read from or
written into the memory address associated with a soft switch. It
is the reference to that address that throws the switch. The data
written to or read from the location has no effect.
Machine language programs should reference the hexadecimal
value
for the memory address associated with the soft switch.
BASIC
programs should use a read operation to the decimal
value for the memory address associated with the soft switch . A
write operation causes such a short pulse that the speaker will
not emit a sound.
The memory address for the soft switch associated with the
speaker is 49200 or hexadecimal C030H. Whenever this address is
referenced in a program, the speaker will emit a small click. By
continually referencing this address, the speaker will generate a
continuous tone.
APPLE lie VIDEO DISPLAY
Monitor/TV Set Connection
The Apple lie can either use a monitor or a regular TV set for
video output. The connection between the lie and a monitor is
simple. Merely use a video cable to connect the video port on the
rear of the lie to the video input port on the monitor. This
connection is depicted in Illustration 1-4.
The
connection between the lie and a TV set is somewhat more
complicated due to the fact that the lle's video signal must be
converted to a signal that can be comprehended by the TV set. A
device known as an RF modulator must be installed in the lie in
order to convert the lle's video signal. The RF modulator is
generally connected to a group of four Molex-type pins on the
rear right-hand side of the main board.
A
switch box is also generally connected to the VHF terminals of
the TV set's antenna box. This switch box enables the TV set to be
operated normally in one setting; while in the second setting, it
serves as the lle's video output device. The installation of the TV
switch box is depicted in Illustration 1-5.