Is one allowed to answer amen to berachos said over the phone?
My wife mentioned to me that in one of the books on Amen there was a story about a Tzadik who used to call the police station so that they could say amen to his brochos.
According to some poskim, one may not answer amen to berachos said over the phone, because one only hears an ‘electronic signal’, and not the berachah itself. However, many maintain that one may (and is obligated to say amen to a berachah over the phone).
Concerning answering amen, one should follow the latter opinion (and answer amen), because the stringency of a blessing in vain does not apply.
Sources: A number of poskim write that one should answer amen, kedushah, and so on, even over the phone: Minchas Elazar II:72; Neta Shaashuim 7; Shaarei De’ah 2. These rulings also apply to reading the Megillah. However, Minchas Shlomo (I:9) writes that one can certainly not answer amen to blessings over the phone, comparing this to a gramophone–a ruling also stated by Be’er Moshe (III:166)–though he records that the Chazon Ish was unsure of the matter. Har Tzvi (9), quoting from Rav Yosef Engel (Megillah 25) writes that in principle one would be able to answer amen, and this ruling is echoed by Iggros Moshe (II:108; IV:126), although he writes that one may not hear the Megillah over the phone. See also Tzitz Eliezer (IV:26) and Yecheveh Daas (III:54).