Petey's phone - an early 2000s style clamshell phone with incredible battery life
Milchick's phone - a bulky but powerful satellite-style phone which enables him to reach the outside world from the deep bowels of Lumon's underbasements
Mark's outie phone - a standard - though non-Apple! - modern smartphone
Natalie's Board earpiece - a clip on headset through which she can hear the Board and convey their wishes to whomever she is interfacing with in person. The Board can hear another speaker directly in front of Natalie clearly through it, so it is quite powerful.
Ms. Cobel's phone - A relatively standard-looking office-style desk phone, except for only having two buttons. One assumes those buttons summon Mr. Milchick, or Security.
The Board speaker - a plug-in blue grilled speaker, reminiscent of the one Charlie uses to talk to his Angels, through which the Board may listen to multiple speakers in a room at once. Generally speaking, they do not contribute to these meetings verbally, but are present at moments of corporate change. This device may or may not have a camera.
Orientation camera/speaker - a plug-in blue grilled speaker similar to that which is used by the Board but which definitely has a camera. Through this lens, the senior staff member and their helper can speak to and watch the responses of the severed employee awakening on the table after their severance procedure.