I help the kids call grandma back and we all have a laugh about it. But the unfortunate encounter with the model 500 hook switch makes me realize: it's no longer possible to hangup a phone.
When I was a kid, we had a bright yellow, rotary Western Electric model 554, the wall-mountable companion to the 500 desk set. Before answering machines, caller id, *69, and eventually smartphone address books allowed us to screen calls quickly, a ringing phone was a pressing matter. It could mean anything: a friend's invitation, a neighbor's request, a family emergency. You had to answer to find out. Telephones rang loud, too, with urgency and desperation. One simply did not ignore the telephone.
In the context of such gravity, the hangup had a clear and forceful meaning. It offered a way of ending a conversation prematurely, sternly, aggressively. Without saying anything, the hangup said something: we're done, go away.
My father took great pride in hanging up our model 554 phone violently when something went awry. An inbound wrong number dialed twice in a row, or an unwelcome solicitor. Clang! The handset's solid mass crashed down on the hook, the bell assembly whimpering from the impact. The mechanical nature of telephones made hangups a material affair as much as a social one. A hangup is something your interlocutor could feel physically as much as emotionally, and something you couldn't downplay either. Like slamming a door or yelling at a child, hanging up a phone couldn't be subdued or hidden.
Unlike today's cellular network, the public switched telephone network was robust and centralized thanks to monopoly. Apart from flukes like my son depressing the hook switch, a disconnected landline call is almost unheard of. By contrast, it's not possible to hang up on someone via smartphone with deliberateness, because it's so much more likely that the network itself will disconnect of its own accord. Every call is tenuous, constantly at risk of failing as a result of system instability: spectrum auctions, tower optimizations, network traffic, and so forth. The infrastructure is too fragile to make hangups stand out as affairs of agency rather than of accident.
Today a true hangup -- one you really meant to perform out of anger or frustration or exhaustion -- is only temporary and one-sided even when it is successfully executed. Even during a heated exchange, your interlocutor will first assume something went wrong in the network, and you could easily pretend such a thing was true later if you wanted. Calls aren't ever really under our control anymore, they "drop" intransitively. The signal can be lost, the device's battery can deplete, the caller can accidentally bump the touch screen and end the call, the phone's operating system can crash. The mobile hangup never signals itself as such, but remains shrouded in uncertainties.