3 ms·
Medium-sized US exchanges were being converted to ESS in the 1980s. I remember the day my busy signal changed from a buzz (350+440 Hz) to a tone (480+620 Hz).
by quesera 2y ago
Medium-sized US exchanges were being converted to ESS in the 1980s.
I remember the day my busy signal changed from a buzz (350+440 Hz) to a tone (480+620 Hz).