SC4x0 Technical manual
Page 12 of 34
SeaCom
Rev
2.00
4. Data & control signals from the exchange
Signals & data are sent from the exchange in different ways. Control signals are issued as 16kHz
burst, where the duration and current state of operation determine how to interpret date. CLIP signals
(Caller Line Information) are issued using FSK.
Line voltage is used to indicate ringing, busy or idle.
4.1 Line voltage & ringing voltage detector
The line interface fund in drawing SCH061212LAF01_xxx page 2 of 3 shows the line interface.
Line voltage and polarity is measured by the processor via U2A and the voltage divider placed across
the line.
Line Voltage
>25 volt dc
Line is idle
<18 volt dc
Line is busy
<5 volt dc
No line
If AC voltage >25Vac @50Hz is detected (pure AC or AC on top of DC), ringing is detected.
There is a 200ms delay before a valid change of state is detected.
4.2 16 kHz control signals
The line interface fund in drawing SCH061212LAF01_xxx page 2 of 3 shows the line interface. 16kHz
signals are filtered through the high pass filter and passed into the detector. The detector input is
compare to a DC level set by the processor. From the hidden menu system, it is possible to adjust
trigger level for the detector. Only I rare cases where noise is disturbing the detector, adjustment of the
16 kHz threshold level is needed or if the detector needs to be disabled. Setting the level to 0% or
100% will disable the detector.
4.3 FSK / CLIP data
If the exchange is programmed to issue FSK data, caller’s ID can be displayed. Data is sent in a single
burst of 575 ms from the exchange, 500ms after first ring signal. FSK data is decoded by U19 and sent
as 1200 baud data 8N1 to the processor. The processor’s UART 1 picks up any FSK data. Up to 20
digits and 50 chars can be sent as caller’s number & name in a single message. The telephone will,
however show the last 16 digits only of the number and the 16 first chars of the name.
The telephone needs no power on / wake up ringing signal as it runs on constant power and never
enters any power down mode. This means data can be received without the need of an alert ringing or
signal sequence.
NOTE: Only month and day data is defined in the time data frame for CLIP data. If year info is needed,
it must be keyed in manually from the menu system. The internal RTC use year info for leap year info.
Default year will be 00. This will have a potential impact on the date shift from 28->29 of feb.
