RFX144V24-S23 and RFX96V24-S23 Modem Designer’s Guide
10-2
1070
The calling party's directory number is represented by the remaining words in the data word field. If the calling party's
directory number is not available to the terminating central office, the data word field contains an ASCII “O”. If the calling
party invokes the privacy capability, the data word field contains an ASCII “P”.
Checksum Word
The Checksum word contains the twos complement of the modulo 256 sum of the other words in the data message (i.e.,
message type, message length, and data words). The receiving equipment may calculate the modulo 256 sum of the
received words and add this sum to the received checksum word. A result of zero generally indicates that the message was
correctly received. Message retransmission is not supported.
Example CND Single Data Message
An example of a received CND message, beginning with the message type word, follows:
04 12 30 39 33 30 31 32 32 34 36 30 39 35 35 35 31 32 31 32 51
04h = Calling number delivery information code (message type word).
12h = 18 decimal; Number of data words (date, time, and directory number words).
ASCII 30, 39 =09; September
ASCII 33, 30 = 30; 30th day
ASCII 31, 32 = 12; 12:00 PM
ASCII 32, 34 = 24; 24 minutes (i.e., 12:24 PM)
ASCII 36 30 39 35 35 35 31 32 31 32 = 609-555-1212; calling party's directory number.
51h = Checksum Word.
R1
R2
To Phone line
RX1
CR1
CR3
CR2
R3
C1
K1
U1
R4
Vcc
Vcc
Vcc
K2
Q1
~OHRC
(Modem off hook
relay control)
To Modem
CNDEN
(To modem
controller)
Normal modem signal path; K1 active
CND signal path; K2 active
Circuitry added for CND
1070F10-1 Call ID Sch
Figure 10-1. DAA Circuit Supporting CND
Содержание RFX144V24-S23
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