Calling Line Identifier
CMX602B
1.6
Application Notes
1.6.1 'On-Hook' Operation
The systems described in this section operate when the telephone set is not in use (on-hook) to display
the number of a calling party before the call is answered.
British Telecom System
Figure 8a illustrates the line signalling and CMX602B I/O signals for the BT on-hook Calling Line ID
system as defined in BT specifications SIN227 and SIN242 part 1. A similar system is described in ETS
300 659-1 section 6.1.2c.
The Tone Alert signal consists of simultaneous 2130Hz and 2750Hz tones, the 'Chan Seize' signal is a
'1010..' FSK bit sequence. Not shown are the requirements for AC and DC loads, including a short initial
Current Wetting Pulse, to be applied to the line 20ms after the end of the Tone Alert signal and to be
maintained during reception of the FSK signal. Note that, for simplicity of presentation, the Data Retiming
function is not used in Figure 8a (RXCK is kept high).
Figure 8a : BT On-hook System Signals
Bellcore System
Figure 8b illustrates the line signalling and CMX602B I/O signals for the Bellcore on-hook Caller ID system
as defined in Bellcore documents GR-30-CORE and SR-TSV-002476 and also in ETS 300 659-1 section
6.1.1.
As for the BT system, the 'Chan Seize' signal is a '1010..' FSK bit sequence. The Bellcore specifications
do not require AC or DC line terminations while the FSK data is being received, however ETS 300 659-1
allows for the possibility of an AC termination being applied. Note that, for simplicity of presentation, the
Data Retiming function is not used in Figure 8b (RXCK is kept high).
2003 CML Microsystems Plc
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D/602B/2
CMLMICRO [ CML MICROCIRCUITS ]
