Dial-Up Modem Handshake

How it's made

Source

an electrical telephone link, compressed into a six-second handshake montage. A 350/440 Hz dial tone precedes six dual-frequency dialing pulses (697-941 Hz plus 1209-1477 Hz).

Carrier

a 2100 Hz answer tone has shallow 15 Hz amplitude modulation; two continuous-phase FSK channels alternate 980/1180 and 1650/1850 Hz, followed by a 1250-2450 Hz training squeal and sidebands.

Training

shaped white noise in 650-3300 Hz bursts alternates with irregular multicarrier symbols; noise colour moves during equalizer training, then falls away to a short, steady lock tone.

Body

a mono telephone path rolls off below 260 Hz and above 1500-3900 Hz. A broad 1450 Hz speaker colour adds small-box presence without a ringing resonance. No room or stereo spread is baked in.

Envelope

dial pulses have 5 ms ramps; carrier sections have 12-35 ms ramps. Noise bursts have 9-35 ms edges; the sequence fades out near its selected length. FSK symbols preserve oscillator phase.

Variation

seeded symbol choices, noise and sub-percent carrier tuning vary the electrical detail. Presets offer a clean connection, a shorter fast link, a noisy retraining line and a muffled speaker.

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