REN booster circuit

[Mike Watterson]

Some thoughts here: https://northcoastsynthesis.com/news/bui...g-booster/

and the electrical interface for telephone instruments hasn't changed in decades.

Apart from tone dialling, not much in over 100 years!
Mysteriously some cable and fibre system will even still work with a rotary dial, or the mad pushbutton phones for ancient exchanges that even had a pulse/tone switch, in pulse mode.

With practice and a suitably reponsive on/off hook switch for the handset it used to be possible to dial a number by tapping. Some places (like digs) had a lock on the dial to stop outgoing calls.