Newer analog telephones (for example, Avaya 62xx series) have buttons with specific functions for placing a call on Hold:

Hold button A hold function that is local to the telephone

Pressing the Hold button causes the analog station to place a hold bridge in both directions at the telephone set. No signaling notification is sent to the SLS call-engine and, therefore, there is no ability to notify the other party that they have been placed on hold. Pressing the Hold button a second time causes the analog phone to remove the hold bridge and the call path is restored. In essence, this hold operation is equivalent to using the Mute button on station sets.

Flash button A function that sends a switchhook signal to the server

Switchhook (receiver on/off hook) A function that sends a disconnect signal to the server