Of course it could still be construed as a lousy sentence because then we couldn't know whether "simultaneously and effectively" modifies "widens" or "pressing", the immediate reaction being, how does one press switches effectively
Effectively can be used (at least) three ways, and I read the word as having meaning (2) of these:
1. Modifying a preceding verb in which case it means "efficiently, productively, in such a way as to achieve the desired results" -
Make sure that resources are used effectively.
How to use PowerPoint effectively.
2. As a substitute for "in effect" -
He stopped taking his medication, effectively making his breakdown occur.
By withholding further funds they effectively killed the project.
By pressing both switches simultaneously you effectively widen the mid-frequency bandwidth.
3. To mean "virtually, really, in fact, essentially, in effect, in reality, in truth, as good as, in actual fact, to all intents and purposes, in all but name, in actuality, for practical purposes" -
The region was effectively independent.
Although small pockets of fighting continued, the battle was effectively over.