Calling Line Identifier with VMWI
CMX612
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 9a illustrates the line signalling and CMX612 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. and ETS 300 778-1.
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 9a (RXCK is kept high).
Figure 9a : BT On-hook System Signals
Bellcore System
Figure 9b illustrates the line signalling and CMX612 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. and ETS 300 778-1.
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
and ETS 300 778-1 allow for the possibility of an ac termination being applied. Note that, for simplicity of
presentation, the Data Retiming function is not used in Figure 9b (RXCK is kept high).
ã 2002 Consumer Microcircuits Limited
14
D/612/3
CMLMICRO [ CML MICROCIRCUITS ]
