May one answer Amen, Kaddish, Kedusha through a Telephone, radio, live video/audio internet hookup?
Some Poskim rule one is not to answer Amen or Kedusha in such circumstances. Other Poskim rule one is to answer Amen and for Kaddish/Kedusha. Practically, one may be lenient in this matter. [If however there is a number of seconds of delay between the “live” hookup and the actual events taking place then according to all opinions one may not answer Amen to a blessing or to Kaddish/Kedusha. In many live broadcasts there are several seconds of delay between the events and the broadcast, and hence in such a case one may not answer Amen to the blessings or Kaddish.]
May one be Yotzei Havdala, Megillah and the like via Telephone; radio; speakers; microphone etc?
 The Halachic issues regarding this question are 1) Is this considered an Amen Yesoma? [Admur 124/11] 2) Must one suspect that there are feces interfering between the answerer and the person saying the blessing? [Admur 55/22]
 Piskeiy Teshuvah 167; Rav SZ”A in Minchas Shlomo 9/1; Moadim Uzmanim 6/105; Mishpitei Uziel 1/5 [brought in Igros Kodesh 13/221as opinion of Sefaradim]; Beir Moshe 3/166-168; See Mishneh Sachir 30; Tzitz Eliezer 20/19; Ratz Katzevi 2/10; Piskeiy Teshuvos 56/3
 The reason: Being that there may be feces or idols that intervene between him and the area that the blessing or Minyan is taking place. [See Admur 55/22; Koveitz Ohalei Sheim 5/104] Alternatively, this is because it is defined as an Amen Yesoma since the person is not in the same room as the person saying the blessing. [Piskeiy Teshuvah ibid; Minchas Shlomo ibid; Moadim Uzmanim ibid] Vetzaruch Iyun Gadol as to why being in a different area would make it an Amen Yesoma, contrary to the explicit ruling in Admur 55/22 based on the Gemara and Poskim
 Minchas Elazar 2/72; Igros Moshe 2/108; 4/91; Yechaveh Daas 2/68; See Igros Kodesh 13/179 and 13/221 and Likkutei Sichos 21/497 [printed in Shulchan Menachem 1/81] that the Ashkenazim [i.e. Minchas Elazar of Hungary] are lenient in this, thus implying that the Rebbe rules like the opinion.
 The reason: This is permitted as a) There is no need to be in the same room as a person in order to answer Amen, [Admur 55/22] Now, although most certainly there are feces or idol worship in-between, nevertheless we are lenient being that the phone wires that carry the voice bypass the feces and idols. This is in addition to that the wires are in the air, higher than ten Tefachim and is thus considered a different Reshus. [Minchas Elazar ibid; See Admur 345/17]b) There is no need to hear the actual voice of the person saying the blessing so long as one knows what blessing he is answering for. [Admur 124/11]
 So seems to be the leaning opinion of the Rebbe ibid; See Piskeiy Teshuvos 56/3 that one may be lenient regarding Amen of a blessing [however not obligatory] however not regarding Kaddish and Kedusha
 Admur 124/11
 Heard from a media technician; Verified through sampling various live broadcasts and seeing a delay between different channels.
 See Admur 124/11 regarding the definition of an Amen Yesoma; Mishpitei Uziel ibid; Piskeiy Teshuvos 215/3
 The reason: If it is not live then there is no greater Amen Yesoma than this. [See Admur ibid]
 Rebbe in Shulchan Menachem 3/319; Daas Torah 689 based on Halachos Ketanos; Mahraiy Engel Brachos 25; Minchas Shlomo 1/9; Eretz Tzvi 1/23; Minchas Yitzchak 1/37 and 3/38; Yechaveh Daas 2/68; 3/54; Mishneh Halachos 4/85; Kinyan Torah 1/75; Igros Moshe 2/108; 4/126 [not to do so initially]; Sheivet Halevi 5/84; Beir Moshe 3/166-168; Piskeiy Teshuvos 689/3
Other Poskim: The following Poskim are lenient are permit hearing the Megillah through a microphone and the like: Minchas Elazar 2/72; Mikraei Kodesh 11; Tzitz Eliezer 8/11; See Igros Moshe ibid that his leaning opinion is to permit being Yotzei and that so should be done in a case of need, that one is unable to hear Havdala otherwise.
 The reason: As a) One may not be Yotzei a blessing unless he hears the actual voice of the person saying it. [Admur 124/11] and b) “What is heard is not a man’s voice at all (and does not even resemble the case of one who sounds a Shofar in a pit). It is obviously most novel, even strange, to suggest that an indirect effect (koach kocho) and a basic transformation of the very nature of speech, should serve as a substitute for speech. Even though the recent scholars who have ruled otherwise include reputed poskim, it is evident from their very responsa that those who explained them the nature and workings of the telephone made a basic mistake.” [Rebbe ibid]
 Conclusion of Admur 124/11 that one is to be stringent like both opinions and according to the first opinion one is not Yotzei if he does not hear the blessing from the person and he thus may not answer Amen due to it being an Amen Yesoma.