The programmable speaker is a circuit network entity that is capable of producing alerts in the form of sound, and elements on nearby players' guis. It can be connected to the circuit network to produce an alert when a signal drops below a certain value, for example. It can be toggled whether the sound plays globally so that it can be heard anywhere on the map, or locally so it will only be audible in the immediate vicinity of the speaker. As a courtesy, only enable global play on multiplayer when it is important that all players be notified. Only 50 sounds can be heard at once due to a game limitation.
As well as playing a sound, it can also be set to send a GUI text alert so the player can see what has caused the alarm. Both text and an icon can be specified.
GUI and configuration
The volume of the programmable speaker can be controlled in the GUI. This determines the audio volume, and the carry distance if global playback is unticked. The range at full volume appears to be 64 tiles.
In order to show an alert in players' GUIs, "Show alert" must be ticked. Additional options will be shown that allow the player to select an icon and text for the alert.
The "Allow polyphony" check-box determines whether more than one sound may be played at once. Essentially, when hooking up a constant signal to a programmable speaker, with polyphony enabled, sounds will repeat extremely rapidly. (10 per second or so) Without polyphony, this is limited to about 1 per half second. Disabling polyphony is useful to avoid alerts being spammed and causing hearing damage. However, if producing music, polyphony may be needed.
The "Circuit value is pitch" check-box allows dynamically changing the pitch of the sound created by changing the circuit value. This is useful for music production. If the player simply wants a sound to be created whenever the conditional is met, they should disable this check-box.