A further characteristic of the Trim-Phone is that the frequency of their tone was exactly in the middle of the ranges where human hearing distinguishes location between sound intensity in each ear and the phase difference of sound waves across the head. Consequently, it was very difficult to work out where the ringing sound (in actuality a warbling) was coming from.
Not only that, blackbirds and starlings loved to imitate the noise which did not help the humans.
Thank ${DEITY} they are no longer common. May they Rust In Pieces.