Geiger Counter operating
Geiger Counter operating
Geiger Counter operating with blips, constant rate
Geiger Counter operating with buzzer
Telephone confidence tones: 1 or 4 or 7 or 0; 2 or 5 or 8; 3 or 6 or 9
Telephone dial tone, 4 figures dialled, busy signal
Telephone dial tone, 4 figures dialled, internal ring, received lifted & replaced
Telephone dial tone, 4 figures dialled, internal ring, receiver replaced; dial tone, 4 figures dialled, internal ring, receiver lifted
Telephone dial tone, 7 figures dialled, ringing, receiver lifted, replaced receiver local end replaced
Telephone dial tone, 9 figures dialled, number unobtainable; dial tone 7 figures dialled, ringing, receiver replaced