Нет бы нам совещаться, мы сразу нажали сигнальную кнопку.

Нет бы is an idiomatic colloquial expression that shows regret, criticism, or “that would have been the sensible thing to do”.

In this sentence, it means something like:

• Instead of discussing things first...
• We should have discussed it first, but no...
• Rather than consulting each other, we immediately pressed the alarm button.

So нет бы does not literally mean there is no here. It is a fixed expression used to criticize what actually happened in contrast with what would have been wiser.

Because нам is in the dative case, and after нет бы Russian often uses:

• нет бы + dative + infinitive

So:

• нам = for us / us to
• совещаться = to discuss / to confer

Literally, the structure is close to:

• It would have been good for us to discuss things first
• or Instead of us discussing things first...

Using мы would not fit this construction.

After нет бы, Russian commonly uses an infinitive to name the action that would have been appropriate.

So:

• нет бы нам совещаться = we should have been discussing things / we should have consulted each other

This is similar to English patterns like:

• Instead of discussing it first...
• We should have discussed it first...

Russian often prefers the infinitive in this kind of evaluative structure.

Совещаться is the imperfective verb, and here it presents the action as a process or general course of action: to confer, to deliberate, to consult together.

That fits the idea of what they ought to have been doing before acting.

Compare:

• совещаться = to be discussing / deliberating
• посовещаться = to have a discussion, to confer for a bit, to consult and finish

In this sentence, the imperfective makes the “proper behavior” sound like the sensible process they should have engaged in.

Yes, that would also be natural.

The difference is subtle:

• совещаться stresses the process of discussing/deliberating
• посовещаться stresses having a discussion as one completed step

So:

• Нет бы нам совещаться... = Instead of consulting/discussing things...
• Нет бы нам посовещаться... = We should have had a discussion first...

Both are possible. The version with посовещаться may sound a bit more like we should have sat down and talked it over first.

The -ся shows that this is a verb meaning to confer among themselves / consult with each other.

So совещаться is not just to discuss something in the abstract, but more specifically:

• to hold a discussion together
• to deliberate collectively
• to consult one another

That is why the reflexive form is used here. It emphasizes a group acting together.

The first part, Нет бы нам совещаться, works like a commenting or reproachful introductory clause, and the second part states what actually happened:

• Нет бы нам совещаться, мы сразу нажали сигнальную кнопку.

This is a very natural Russian way to set up a contrast:

• what would have been better vs.
• what we actually did

In English, we often need extra words such as:

• Instead of discussing it first, we immediately pressed the alarm button.
• We should have discussed it first, but instead we immediately pressed the alarm button.

Russian can do this very compactly with a comma.

Нажали is the past plural of the perfective verb нажать, meaning to press as a completed action.

That fits the situation well:

• they pressed the button once
• the action is viewed as completed
• it happened immediately

If Russian used the imperfective нажимали, it would suggest something different, like repeated pressing, an ongoing action, or focus on the process rather than the single completed event.

So мы сразу нажали means:

• we immediately pressed it
• we went ahead and pressed it right away

Сразу means right away / immediately / at once.

It strengthens the contrast between:

• the sensible thing: совещаться
• the actual thing: сразу нажали кнопку

So the sentence has a reproachful tone like:

• Instead of discussing it, we just immediately hit the button.

It makes the action sound hasty.

Grammatically:

• кнопку is accusative singular, because it is the direct object of нажали
• сигнальную agrees with кнопку in gender, number, and case

Lexically, сигнальная кнопка is literally signal button. Depending on context, it may be translated as:

• alarm button
• emergency button
• signal button

A native English translation often depends on the situation rather than on the Russian words alone.

It is fairly colloquial, especially because of нет бы, which is a very conversational, emotionally colored expression.

It sounds like someone complaining, criticizing, or looking back on a bad decision:

• We should have done X, but instead we did Y.

The rest of the sentence is neutral enough, but нет бы gives it a distinctly spoken, natural, slightly reproachful tone.

The tone is self-critical, reproachful, and a bit frustrated.

The speaker is not simply stating two facts. They are saying that:

• there was a better, more sensible thing to do
• but they failed to do it
• and acted rashly instead

So the tone is close to:

• If only we had talked it over first...
• We really should have discussed it instead of acting immediately.

That emotional coloring is one of the main reasons Russian uses нет бы here.