caller ID. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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caller ID. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Telephony

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Caller ID(CID) is a telephone service, it allows using a special device or modem that supports Caller ID, to get the number of the caller, as well as the date and time. The subscriber must contact the telephone company to order this service.

Identification of the number by the Caller ID system is possible if the PBX of the called and calling subscriber support CID. If the connection is made through transit exchanges, then they must also support this service. Information about the number is received from the PBX of the calling subscriber to the PBX of the called party when transmitting connection request data, then the PBX of the called subscriber sends him information about the calling subscriber's number, time and date during a 4-second pause between the 1st and 2nd call parcels.

Caller ID transmits data in binary system, bits are combined into bytes of 8 bits, each byte is limited by the start and end bits. The transfer is made with the following parameters:

Baud rate ............................... 1200 bps
Label (logic 1).................................. 1200 (+/-12) Hz
Space (logical 0) .............................. 2200 (+/-22) Hz
Transmission level at 900 ohm impedance .................. 13.5 dBm

Data transfer protocol:

1)	Channel capture signal - 30 continuous bytes 55h (01010101). Serves to check the performance of this function at the determinant.
2)	Courier signal - 1200 Hz, 130 (+/-25) ms. Serves to create conditions for receiving information.
3)	Caller information:
3.1)	Data type - CID - 04h (00000100)
3.2)	Byte indicating the length of information (total number of bytes) from 3.3 to 3.7
3.3)	Two bytes indicating the month in ASCII encoding
3.4)	Two bytes indicating the day of the month in ASCII encoding
3.5)	Two bytes indicating the local ASCII hour
3.6)	Two bytes indicating the minute of the hour in ASCII encoding
3.7)	Called subscriber number in ASCII code, if instead of number:
	O - number not defined
	P - the caller has restricted caller identification
3.8)	A byte indicating the checksum. Serves to check the correctness of the received information. With correct transmission and reception 3.8 = sum of bytes from 3.1 to 3.7

An example of receiving information from Caller ID

Let us give an example of the information received from the ATS (point 3). The following data has been received:
04 12 30 39 33 30 31 32 32 34 36 30 39 35 35 35 31 32 31 32 51 (Hex).

04h ........................................ information type - Caller ID (CID ) 12h ............................................ number of bytes of the date, time, numbers - 18 30h,39h (ASCII "09") ............................. month - September 33h,30h ( ASCII "30") ................. day - 30th 31h,32h (ASCII "12 ") .................. hour - 12:xx 32h,34h (ASCII "24") ............................... minute - xx:24 36h,30h,39h,35h,35h,35h,31h, 32h,31h,32h (ASCII "6095551212") .............. number - 609 5551212 51h ....... ......................................... Checksum word

Caller ID will display the following information: SEP 30 12:24 (609) 5551212.

Publication: cxem.net

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