Eagle used to make the bedhead units. They were 100v with about half a watt tapping, channel selector and volume controls. Much the same as was used for hospital radio to bedhead units using stethosets.
I think I saw a hotel with a version with an alarm buzzer, I think you turned rotary switches to select the hour and minutes in 5-min segments - so probably 2 x 12-way rotary switches - with 24 wires plus a common back to a central controller (something like a uniselector probably) that energised the appropriate hour and minute wire, paralleled to all rooms.
American schools used to have a similar system, usually one channel for programme, intercom and all-call.
https://www.bogen-paging.com/catalog-product-pi35a.aspx
In one of my public address books there is a description of hotel systems that relayed music from the ballroom as well as radio programmes, and guests could rent a key from reception to turn the bedroom speaker on, or put coins in a slot, if the music wasn't free.
Gaitronics used to make one for accommodation units in oil rigs. Their unit had a detector circuit which responded to a permanent supervisory tone; if the tone was lost for any reason the unit defaulted to channel 1 at max volume for emergency announcements. That might have been a locally-tuned FM radio as I think it used a single coax for programme feed.
A more modern eqquivalent
http://www.ziztel.com/bed-head-units.php