Supondo que eles estivessem usando CCTV (muito provavelmente eles eram), o CCTV pode ser transmitido e inventado em 1940, então estava disponível na década de 1970.
Closed-circuit television (CCTV), also known as video surveillance, is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors. It differs from broadcast television in that the signal is not openly transmitted, though it may employ point to point (P2P), point to multipoint, or mesh wireless links. Though almost all video cameras fit this definition, the term is most often applied to those used for surveillance in areas that may need monitoring such as banks, casinos, airports, military installations, and convenience stores. Videotelephony is seldom called "CCTV" but the use of video in distance education, where it is an important tool, is often so called.[1][2]
Não tenho certeza sobre a distância CCTV (não sei nada sobre a tecnologia), mas sei que ele não viveu muito longe da faixa.
E se nada mais, poderia ter sido entregue via cabo
Beginning almost simultaneously in Arkansas, Oregon and Pennsylvania in 1948, cable originally brought distant over-the-air television signals from miles away to mountainous or geographically remote areas. In the 1960s and 1970s, cable TV expanded into bigger cities and major metro areas.