Is it safe to wire a telephone to a breadboard?
In Europe the ring signal is 90 Volts RMS.
DC voltage greater than 50 V or AC peak voltage greater than 42 Vpeak are considered hazardous by IEC and by UL.
That means that you have to be careful.
Back in 1999 while I was prototyping a 2400 bps modem based on a TDK integrated transceiver, I got the ring signal on my fingers and I can tell you that it wasn't nice.