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Chapter 16

Signaling System Number 5 Protocol

16.1 Signaling Overview

: 16.1.1 Signal Exchange

16.2 Parameters

: 16.2.1 Editable Parameters
: 16.2.2 Non-editable Parameters

16.3 Special TCP Behavior

: 16.3.1 Inbound Calls: Retrieving Digits All at Once
: 16.3.2 Inbound Calls: Retrieving Digits One at a Time
: 16.3.3 Outbound Calls: Digit Format

Introduction

This chapter provides the following information: Overview of signaling performed by the Signaling System 5 protocol, implemented by the SS5 TCP SS5 TCP parameters Operations specific to the SS5 TCP within the framework of Natural Call Control.
The SS5 TCP implements the CCITT Recommendations Q.140-Q.164, "Specifications of Signaling System No. 5", CCITT Red Book, Volume VI, Fascicle VI.2, Geneva 1985.

16.1 Signaling Overview

SS5 line signaling is performed by in-band compelled single or dual-frequency tones. Two frequencies are used, either alone or in combination: f1 = 2400 Hz, and f2 = 2600 Hz. These frequencies are sufficiently far apart from the register signaling tones not to cause any false detection, and are in a frequency band where the likelihood of a false detection due to voice is minimal.
Since no signaling bits are involved, this is not strictly a digital CAS protocol, but can be used on analog trunks as well. However, Natural MicroSystems implementation is for digital boards. Note: The SS5 protocol can be used to set up calls on both T1 and E1 trunks.
The following table illustrates line signaling for a typical call. State Forward tone Direction Backward tone Idle None None Seizure f1 (2400 Hz) Proceed to send \xdf f2 (2600 Hz) Here the outbound side starts to send the address information. This is accomplished by in-band MF tones. Call setup continues with the inbound side playing a ring-back tone, if the call is accepted, and then answering the call. Ringing \xdf Ring tone Answer \xdf f1 (2400 Hz) Answer acknowledge f1 (2400 Hz) If the inbound side rejects the call instead, the tone played is different Busy-flash \xdf f2 (2600 Hz) Busy-flash acknowledge f1 (2400 Hz) Idle None None It is also possible that busy-flash tone not be played at this time to reject a call. In this case the busy tone of the target network is played instead. Depending on which of the sides hangs up the call first, we have a clear back signal, or a clear forward signal. A clear back signal must be acknowledged by the outbound side, then a clear forward signal is sent, acknowledged by a release guard signal. Idle follows. Inbound hangs up first: Clear back \xdf f2 (2600 Hz) Clear back acknowledge f1 (2400 Hz) Pause: Two consecutive signals in the same direction 100 ms minimum Clear forward f1 + f2 (2400+2600 Hz) Release guard \xdf f1 + f2 (2400+2600 Hz) Idle none none Outbound hangs up first: Clear forward f1 + f2 (2400+2600 Hz) Release guard \xdf f1 + f2 (2400+2600 Hz) Idle None None

State	Forward tone	Direction	Backward tone
Idle	None		None
Seizure	f1 (2400 Hz)
Proceed to send		\xdf	f2 (2600 Hz)
Here the outbound side starts to send the address information. This is accomplished by in-band MF tones. Call setup continues with the inbound side playing a ring-back tone, if the call is accepted, and then answering the call.
Ringing		\xdf	Ring tone
Answer		\xdf	f1 (2400 Hz)
Answer acknowledge	f1 (2400 Hz)
If the inbound side rejects the call instead, the tone played is different
Busy-flash		\xdf	f2 (2600 Hz)
Busy-flash acknowledge	f1 (2400 Hz)
Idle	None		None
It is also possible that busy-flash tone not be played at this time to reject a call. In this case the busy tone of the target network is played instead.
Depending on which of the sides hangs up the call first, we have a clear back signal, or a clear forward signal. A clear back signal must be acknowledged by the outbound side, then a clear forward signal is sent, acknowledged by a release guard signal. Idle follows.
Inbound hangs up first: Clear back		\xdf	f2 (2600 Hz)
Clear back acknowledge	f1 (2400 Hz)
Pause: Two consecutive signals in the same direction	100 ms minimum
Clear forward	f1 + f2 (2400+2600 Hz)
Release guard		\xdf	f1 + f2 (2400+2600 Hz)
Idle	none		none
Outbound hangs up first: Clear forward	f1 + f2 (2400+2600 Hz)
Release guard		\xdf	f1 + f2 (2400+2600 Hz)
Idle	None		None

16.1.1 Signal Exchange

The signals are exchanged following a compelled scheme. The exchange goes as follows: Side A starts playing a tone When side B detects the tone, it starts playing its tone. When side A detects side B's tone, it stops playing its tone. When side B detects silence, it stops playing the tone it was playing.
Thus, there is no fixed timing, but the whole cycle proceeds at the maximum speed allowed by the tone detection and generation equipment.
Register signaling is implemented by in-band MF tones, that the outbound equipment sends to the inbound equipment. These tones are unacknowledged. The relevant address is preceded by a "KP" tone (start-of-pulsing) and ended by a "ST" tone (end-of-pulsing).

16.2 Parameters

The SS5 TCP is programmed by the parameters described below to implement the specifications of all supported countries and network operators. Caution: Most of the parameters that follow are signaling-specific: changing their value would not only invalidate any approval certificate for the used board, but would also most likely cause the board to malfunction. These parameters are described here for reference purposes only.
Other parameters program the interaction the TCP has with the host, or act on features not regulated or that can change from switch to switch within the same network. These are changeable, and indeed, the application developer is often asked to do so.

Caution:	Most of the parameters that follow are signaling-specific: changing their value would not only invalidate any approval certificate for the used board, but would also most likely cause the board to malfunction. These parameters are described here for reference purposes only.

16.2.1 Editable Parameters

Users can modify the following ADI.SS5 parameters: Field Name Type/Unit Default Description numdigits number 7 Relevant to inbound protocol. Specifies the number of incoming digits to expect. Note: this is overridden if the outbound party sends a ST (end of dialing) tone. A ST tone is foreseen in the CCITT specifications, but can be missing. optionflags mask 0x1 Relevant to inbound protocols. Flags controlling optional TCP behavior: · bit 0 (&0x1): Variable number of incoming digits: notify the host of an inbound call if a timeout occurs during digit reception (if 1), or reject the call (if 0). Note that this is only valid if the ST tone is missing. · bit 1(& 0x2): Set this bit if you need to play a message while rejecting a call. If the bit is set, the TCP will not send to the network the "busy flash" clearback signal to reject the call, but will wait for a clear forward signal while the application plays the message,. debugmask mask 0x0 Specifies what trace messages are generated (run agtrace 1000 or higher to see them): · 0x01: Show all states as they are entered · 0x02: Show sent and received digits · 0x04: Show signaling bits · 0x08: Print a description of timeout- related errors These values can be ORed for cumulative effect.

Field Name	Type/Unit	Default	Description
`numdigits`	number	`7`	Relevant to inbound protocol. Specifies the number of incoming digits to expect. Note: this is overridden if the outbound party sends a ST (end of dialing) tone. A ST tone is foreseen in the CCITT specifications, but can be missing.
`optionflags`	mask	`0x1`	Relevant to inbound protocols. Flags controlling optional TCP behavior: · `bit 0 (&0x1): Variable number of incoming digits: notify the host of an inbound call if a timeout occurs during digit reception (if 1), or reject the call (if 0). Note that this is only valid if the ST tone is missing.` · bit 1(& `0x2`): Set this bit if you need to play a message while rejecting a call. If the bit is set, the TCP will not send to the network the "busy flash" clearback signal to reject the call, but will wait for a clear forward signal while the application plays the message,.
`debugmask`	mask	`0x0`	Specifies what trace messages are generated (run `agtrace 1000 or higher to see them):` · `0x01: Show all states as they are entered` · `0x02: Show sent and received digits` · `0x04: Show signaling bits` · `0x08: Print a description of timeout- related errors` These values can be ORed for cumulative effect.

16.2.2 Non-editable Parameters

The following ADI.SS5 parameters are country or network-specific, and cannot be modified. Parameter name Type/ Unit Example Description Line signaling timers - during different phases of the protocol. intersignaltime ms 100 The minimum time between two line signals in the same direction. Must be kept for signal qualification reasons. longqualtime ms 125 Qualification time of almost all signaling tones. A tone must be present on the line for at least this duration to be recognized. shortqualtime ms 40 Qualification time of the seizure / proceed to send compelled signal. It is shorter to minimize the possibility of glare. connectqualtime ms 1000 Qualification time during the connected phase of a call. It is longer to minimize the possibility of talkoff (voice being erroneously recognized as a line signal). glarewaittime ms 850 Time to wait for the seizure signal to stop, if glare occurs. If an outbound protocol seizes the line by playing a seizure tone, and subsequently recognizes a tone on the line that is not the proceed-to-send tone, it must wait for this time for the other tone to stop. signalcompelledtime ms 10000 First compelled signal maximum duration. ackcompelledtime ms 4000 Acknowledgment compelled signal maximum duration. compelledtoneslevel IDU 250 Amplitude of compelled line signaling tones. Inbound answer phase parameters waitforPCtime ms 30000 Inbound: Specifies the time to wait for the host to answer after an inbound call event has been sent. ringfreq1 Hz 440 Inbound: Specifies the first ring tone frequency. ringfreq2 Hz 480 Inbound: Specifies the second ring tone frequency. ringontime ms 1000 Inbound: Specifies the time the ring tone is on in a ring cycle. ringofftime1 ms 4000 Inbound: Specifies the duration of the first or only time the ring tone is off in a ring cycle. ringofftime2 ms 0 Inbound: Specifies the duration of the second time the ring tone is off in a ring cycle (if there is a second period of silence). busyfreq1 Hz 480 Inbound: Specifies the first busy tone frequency. busyfreq2 Hz 620 Inbound: Specifies the second busy tone frequency. busyontime ms 500 Inbound: Specifies the time the busy tone is on in a busy cycle. busyofftime ms 500 Inbound: Specifies the time the busy tone is off in a busy cycle. fastbusyontime ms 250 Inbound: Specifies the time the congestion tone is on. fastbusyofftime ms 250 Inbound: Specifies the time the congestion tone is off. CPtoneslevel IDU 350 Inbound: Amplitude of the call progress tones. Register signaling timers for the inbound protocol waitKPtime ms 7000 Inbound: Max time to wait after seizure acknowledge for the KP "start of dialing" digit to arrive. waitdigittime ms 8000 Inbound: Max time to wait for every next digit. Register signaling parameters for the outbound protocol outdialdelay ms 100 Outbound: Time to wait after receiving the proceed-to-send signal, before starting to dial KPandSTontime ms 100 Outbound: Duration of the KP and ST tones MFtoneontime ms 55 Outbound: Duration of MF tones MFtoneofftime ms 55 Outbound: Duration of silence between MF tones MFtoneslevel IDU 352 Outbound: Amplitude of MF tones outboundguardtime ms 300 Outbound: Time after an outbound call in which the TCP will not place another call

Parameter name	Type/ Unit	Example	Description
Line signaling timers - during different phases of the protocol.
`intersignaltime`	ms	`100`	The minimum time between two line signals in the same direction. Must be kept for signal qualification reasons.
`longqualtime`	ms	`125`	Qualification time of almost all signaling tones. A tone must be present on the line for at least this duration to be recognized.
`shortqualtime`	ms	`40`	Qualification time of the seizure / proceed to send compelled signal. It is shorter to minimize the possibility of glare.
`connectqualtime`	ms	`1000`	Qualification time during the connected phase of a call. It is longer to minimize the possibility of talkoff (voice being erroneously recognized as a line signal).
`glarewaittime`	ms	`850`	Time to wait for the seizure signal to stop, if glare occurs. If an outbound protocol seizes the line by playing a seizure tone, and subsequently recognizes a tone on the line that is not the proceed-to-send tone, it must wait for this time for the other tone to stop.
`signalcompelledtime`	ms	`10000`	First compelled signal maximum duration.
`ackcompelledtime`	ms	`4000`	Acknowledgment compelled signal maximum duration.
`compelledtoneslevel`	IDU	`250`	Amplitude of compelled line signaling tones.
Inbound answer phase parameters
`waitforPCtime`	ms	`30000`	Inbound: Specifies the time to wait for the host to answer after an inbound call event has been sent.
`ringfreq1`	Hz	`440`	Inbound: Specifies the first ring tone frequency.
`ringfreq2`	Hz	`480`	Inbound: Specifies the second ring tone frequency.
`ringontime`	ms	`1000`	Inbound: Specifies the time the ring tone is on in a ring cycle.
`ringofftime1`	ms	`4000`	Inbound: Specifies the duration of the first or only time the ring tone is off in a ring cycle.
`ringofftime2`	ms	`0`	Inbound: Specifies the duration of the second time the ring tone is off in a ring cycle (if there is a second period of silence).
`busyfreq1`	Hz	`480`	Inbound: Specifies the first busy tone frequency.
`busyfreq2`	Hz	`620`	Inbound: Specifies the second busy tone frequency.
`busyontime`	ms	`500`	Inbound: Specifies the time the busy tone is on in a busy cycle.
`busyofftime`	ms	`500`	Inbound: Specifies the time the busy tone is off in a busy cycle.
`fastbusyontime`	ms	`250`	Inbound: Specifies the time the congestion tone is on.
`fastbusyofftime`	ms	`250`	Inbound: Specifies the time the congestion tone is off.
`CPtoneslevel`	IDU	`350`	Inbound: Amplitude of the call progress tones.
Register signaling timers for the inbound protocol
`waitKPtime`	ms	`7000`	Inbound: Max time to wait after seizure acknowledge for the KP "start of dialing" digit to arrive.
`waitdigittime`	ms	`8000`	Inbound: Max time to wait for every next digit.
Register signaling parameters for the outbound protocol
`outdialdelay`	ms	`100`	Outbound: Time to wait after receiving the proceed-to-send signal, before starting to dial
`KPandSTontime`	ms	`100`	Outbound: Duration of the KP and ST tones
`MFtoneontime`	ms	`55`	Outbound: Duration of MF tones
`MFtoneofftime`	ms	`55`	Outbound: Duration of silence between MF tones
`MFtoneslevel`	IDU	`352`	Outbound: Amplitude of MF tones
`outboundguardtime`	ms	`300`	Outbound: Time after an outbound call in which the TCP will not place another call

16.3 Special TCP Behavior

The following sections describe operations specific to the SS5 TCP within the framework of Natural Call Control

16.3.1 Inbound Calls: Retrieving Digits All at Once

With SS5 TCPs, after ADIEVN_INCOMING_CALL is received, the calledaddr field in the ADI_CALL_STATUS structure contains all received digits. The callingaddr, usercategory and tollcategory fields are NULL.
The parameter ADI.SS5.digitnumber determines the number of digits the TCP should expect from the calling party. The default is 7.

16.3.2 Inbound Calls: Retrieving Digits One at a Time

The SS5 TCP does not recognize ANI or category digits. Digits are presented in the order in which they arrive. The ADI.SS5.digitnumber parameter determines how many digits to expect, but is active only if the outbound party does not send a "ST" tone (end of dial) at the end of register signaling.

16.3.3 Outbound Calls: Digit Format

Two "KP" digits are possible in the SS5 protocol. These are KP1 ("D", the starting digit for national calls), and KP2 ("E", the starting digit for international calls).
KP1 is the default KP tone, so if the application wants to use KP1 as the starting digit, SS5 TCPs expect the digit string to be formatted as follows:
d1 dn
However, if the application wants to send a different KP digit, the digit string must be formatted as follows:
# KP# d1 dn (where # is a conventional NMS separator)
ANI and category indicators are not used in SS5 TCPs.

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