PTT Station Voice Mirror
Paris, France
1972 Recording

The French telecommunications voice mirror (looped tape announcement) was well known and regularly heard, even "Downunder" in Australia. Interestingly, at the time of this recording (Nov, 1972), Solar Cycle #20 had begun its slow decline. The cycle lasted 11.4 years, beginning in October 1964 and ending in March 1976. Comparison with other cycles shows that geomagnetic activity during the declining phase of cycle 20 (1973–1975) was unusually high. [1]

For example, just three months before this recording was made, an extremely active region, McMath 11976, produced a historic series of solar flares and coronal mass ejections (CMEs) in August 1972. One CME travelled to Earth in a record low of 14.6 hours and produced a strong geomagnetic storm that caused widespread electrical and communications grid disturbances and the accidental detonation of numerous U.S. Navy magnetic sea mines in North Vietnam. [2]

This strong solar activity during 1972 may account for the excellent reception of this Paris PTT station on 20233 kHz (just below the 15-meter band) at 0555 UTC on November 18, 1972. This video below has the recorded audio and my subsequent verification letter received from the Chief Engineer at the Postes et Télécommunications, Direction des Services Radioélectriques, in Paris:

References:

[1] Gosling, J. T.; Asbridge, J. R.; Bame, S. J. (1 August 1977). "An unusual aspect of solar wind speed variations during solar cycle 20". Journal of Geophysical Research. 82 (22): 3311–3314.

[2] Wikipedia