The output voltage is connected to a DPDT switch so Vout
alternates between +2.0 V and -2.0 V as the switch is changed.
The input voltage comes from a 9V battery connected by a mini-phone jack (seen at right below).
Parts list from Radio Shack
Project Box, 270-1801
Circuit Board, 276-149
LM317T adjustable voltage regulator, 276-1778
150 ohm, 271-1312
470 ohm, 271-1317 (90 ohm is 470, 470, and 150 ohm in parallel)
DPDT Switch, 275-663
Mini phone jacks, 274-251C