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Practice with oscill -
Telecommunication
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FSK signals used by wired communication equipment for Caller ID, SMS and others purposes.
On-hook FSK-packet Caller ID (wav, 85kB):
From ETS 300 659-1:
- first 250 ms. Channel Seizure Signal: shall consist of a block of 300 continuous bits of alternating "0"s and "1"s. The first bit to be transmitted shall be a "0". The last bit to be transmitted shall be a "1". It shall start the data transmission only in "on hook" data transmission.
- next 150мс. Mark Signal: shall either consist of a block of 180 ± 25 mark bits or, as a network operator option, Mark Signal may consist of 80 ± 25 mark bits.
- Other - data: Message type, Message length, presentation layer message, Checksym
Channel Seizure (10ms delay from packet start):
 
Mark Signal (300ms delay from packet start):
 
Data (700ms delay from packet start):
 
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