Reference13r1:Interfaces/FXS/Signaling

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There are also other versions of this article available: Reference | Reference9 | Reference11r1 | Reference13r1 (this version)

The call signalling settings of the analogue FXS interfaces can be adjusted here:

Disable: Disables the relevant analogue FXS interface.
Speech Bearer Capability: Calls on the relevant interface are transmitted with Audio Bearer Capability as standard.
A checked check box transmits calls from the relevant interface with Speech Bearer Capability. This only makes sense if only telephones are operated on the relevant interface (no fax machine or modem).
Busy on Busy / No Call Waiting: A checked check box disables the call waiting signal for waiting calls on the relevant interface. Instead, Call busy is signalled to the calling side. This is necessary if, for example, a fax machine is operated on the relevant interface.
Note that call waiting is generally only possible if 'feature codes' are enabled for this interface. It might be neccessary to switch on the 'call waiting' functionality explicitly with *43#.
This checkmark refuses 'call waiting' even if activated within 'feature codes' and is a safe setting especially for fax machines.
Passive: Transfers the relevant interface to the passive mode. As a result, the Flash/Hook signal (R key) is not evaluated.
No Call Transfer on Hook-On: A checked check box disables the call transfer function. Per default calls will be transfered on hook-on. Afterwards a call has been established, this call can be held and a new call can be initiated by pressing the R-Key. If the new call has been established or is yet ringing, the held and new call can be transferred together by hooking on the handset.
There is a special exception : When the second call comes by call waiting, what means, that you have your first call currently on hold, hooking on will NOT transfer the call waiting call with the previous, because this looks like an accident. If you really want to connect them you have to do this by 'R-4'. Hooking on will disconnect the call waiting call and the currently hold call will ring again (for 5 sec). If you use 'R-2' to switch between the call waiting call and the held call, this limitation is cleared and you may now transfer both calls together again by just hooking on.
Signaling tones audibility: In normal operation in-band signaling tones are provided like well known from any phone provider. When the a/b is used in conjunction with a DOOR-Interface Converter, it may be desirable that the disconnect signaling tones at the end of a call are not audible to the person at the door. Checking 'in call establishing phase only' does so, but does not suppress the signalling tones in call establishing phase. This implies that the person at the door will hear typical telephone sounds after pressing the doorbell-button. This mode additionally disables recognition of flash (R) pulses. Checking 'never/silent' additionally supresses singalling tones in call establishing phase, so that there will be no audible telephone sounds at all to the person at the door. This mode disables recognition of flash (R) AND DTMFs as well. This might be the typical choice for DOOR-Interfaces.
Reverse polarity in conversation/connected state: If checked, the gateway will reverse the line polarity to 'conversation/connected state polarity' as soon as the connection to the peer side is established. As a result of this, the line polarity returns to normal polarity again if the peer hooks up the connection. In addition a busy tone is provided. Equipment connected to the FXS port may take advantage of this additional information and safely detect call state details.
Volume: Sets the output volume to the relevant interface (from IP to FXS), in decibel (dB), between -32dB and +32dB. No value or the value 0 is equal to the factory settings.
Metering pulse every: The gateway can generate periodic metering pulses in fixed intervals of time. The value specified here is the time between two successive pulses. A value of 0 or no value disables pulse generation.
Note that metering pulses are only generated for outgoing calls. The first metering pulse is generated when the call is connected. Note also that enabling pulse metering implicitly switches on Passive and No Call Waiting, so that no call can be held and no incoming caller is accepted within a call.
Caller ID 1 standard: CallerId/CLIP can be sent in different ways depending on the country. The basic difference is the type of modulation used. Possibilities are DTMF (Dual Tone Multiple Frequency) and FSK (Frequency Shift Keying). FSK modulation splits up into the Telcordia/Bellcore and ETSI scheme. DTMF modulation has several subsidaries and differ in special digits preceding and succeeding the number information.


Examples using 1234567890 as calling number :
ETSI DTMF : A1234567890C or D1234567890C
Danish DTMF : A1234567890* or D1234567890*
Indian DTMF : 1234567890
Brazilian DTMF : A11234567890C or AB1234567890C
The gateway will add these additional digits to the calling number as shown above, depending on the standard selected.

Country specific exceptions: This topic list countries that define some exceptions in handling specific events.


In Brazil Flash events with a duration of less than 140ms have to be handled as illegal and are therefore ignored.