AMPS: Make pitch, cadence and presentation indicator configurable #18
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It would be nice to make make pitch, cadence and presentation indicator configurable. Proposal - use prefixes or suffixes of the called number to set parameters. Maybe some other mechanism can be used.
As per http://osmocom-analog.eversberg.eu/docs/TIA_EIA_553_A.compressed.pdf
page 109:
This 8-bit field comprises two subfields: pitch, the two most-significant bits, and
cadence, the six least-significant bits. Pitch represents a distinction between tones,
usually based on frequency. Cadence is the on/off pattern of the tones. Standard
Alert is pitch ‘00’in combination with cadence ‘000001’. If the mobile station
supports distinctive alerting, it should generate the pitches and cadences
recommended in the following table
Page 110 describes "Presentation indicator", which controls how AMPS MS should or should not be displaying calling number, if available at all.
I have tested pitch, cadence and presence indicators on some AMPS capable phones I have by changing some variables and recompiling.
As a rule of a thumb, if a phone has LCD screen (and it's probably digital/dual standard) than it can support distinctive ring.
This is auxiliary function to caller id. Motorola StartTAC with one line of alpha LED indicators is capable of caller id display but completely ignored call cadence. StarTAC "digital" with graphical LCD did change cadence (and probably pitch). So did Nokia 6560.
Long story short, all approximately pre-1998 AMPS phones are not capable of caller id and don't use this feature. Those that support are usually more modern and can fallback into AMPS analog mode for backwards network comparability.