I am a newbie and I'm trying to build this pre-amplifier circuit but I don't know what one of the symbols mean. Does anyone know what that switch in the middle is supposed to be? I think its some kind of push button but there seems to be more to it than just a push button.

The image is here:
http://i44.tinypic.com/2zzkgt1.jpg

P.S.

Theres the squares with the circles in them labeled JP1 & JP2 anyone know what those are?

 

JP stands for Jumper....


And yes it is a switch, a double pole single throw (SPDT), with one normally closed contact and one normally open contact.

B. Morse

 

The switch, as depicted, is probably an analog switch, but it really doesn't matter as it will work the same if you use a toggle switch or just hardwire pin-3 to either pin 12 or pin 13. What this is, is a programmable gain setting on the INA110, which is a gain of 10, 100, 200, or 500, when you connect pin-3 to either pins: 13, 12, 16, or 11 respectively. Although it's best not to use long wires to a toggle switch. If you need selectable gain, then I recommend using a 4016 or 4066 analog switch IC located close to the INA110. The logic inputs to the 4066 can be long wires to a selector switch or to toggle switch(es). If you know which gain setting you want or need, then you don't need a switch at all and simply hardwire the INA110 pin-3 to the proper gain select pin as I described above.

Good luck,
Kamran Kazem