The Echo I-class submarines were incapable of accommodating the targeting radar for the anti-ship version, and were not equipped with missiles after the land-attack variant was withdrawn, probably in the mid-1960s when sufficient nuclear-powered ballistic missile submarines (SSBNs) became available.
ðɪ ˈɛkoʊ aɪklˈæs sˈʌbmɚɹˌiːnz wɜːɹ ɪŋkˈeɪpəbəl ʌv ɐkˈɑːmədˌeɪɾɪŋ ðə tˈɑːɹɡɪɾɪŋ ɹˈeɪdɑːɹ fɚðɪ ˈæntaɪʃˈɪp vˈɜːʒən, ænd wɜː nˌɑːt ɪkwˈɪpt wɪð mˈɪsəlz ˈæftɚ ðə lˈændɐtˈæk vˈɛɹiənt wʌz wɪθdɹˈɔːn, pɹˈɑːbəbli ɪnðə mˈɪd nˈaɪntiːnhˈʌndɹɪd sˈɪksti z wɛn səfˈɪʃənt nˈuːklɪɹpˈaʊɚd bɐlˈɪstɪk mˈɪsəl sˈʌbmɚɹˌiːnz ˌɛsˌɛsbˈiːˌɛnˈɛs bɪkˌeɪm ɐvˈeɪləbəl.