Pioneer tuning fork Service Manual page 11

h) Tact Switch
This is A kind of digital switches and is popularly used in
key input circuits for digital ICs including microcomputer
ICs. Voltage drop by the contact resistance in this switch
is negligible because the applied voltage is low (5V — 15V)
and the current is small in digital circuits. Therefore, com­
paratively high-resistance conductive rubber is popularly
used in place of a metal piece. The resistance of metal con­
tacts is less than one o h m and that of conductive rubber
is mostly several hundreds ohms. This has one contact and
one circuit. Some switches among those employing con­
ductive rubber directly opens and closes a part of gilded
copper pattern of a printed circuit board.
i) Other Switches
The variations of the above switches are:
• Flexible switch (remote control switch): A variation of
rotary and push switches which employs a flexible wire
for transmitting push-pull force or torque.
• Reed Switch: This has two overlapping magnetic reeds.
It keeps an air gap between free reed ends. The reeds
Photo 9 Tact Switches
attract each other when magnetic induction is applied.
This is the switch portion of the relay discussed later.
• See-saw Switch (rocker switch): Populary used as a pow­
er switch years ago. This is omitted here because this
is not popular now.
Photo 10 Other Switches a,b,c
Metal
spring
contact
Terminals
Terminals
Fig. 9 Structure of Tact Switch
Insulating rubber
Conductive rubber
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