9.1 Introduction

9.2 Capability Mask

9.3 Signaling Overview

9.4 Parameters

9.4.1 Editable Parameters

9.4.2 Non-editable Parameters

9.1 Introduction

This chapter describes the Digital Ground Start signaling protocol and TCP parameters. It provides the following information:

• Digital Ground Start signaling overview.

• Digital Ground Start TCP parameters.

• Operations that are specific to the Digital Ground Start protocol within the framework of Natural Call Control.

Although ground start protocols exist in both analog and digital variations, the Natural MicroSystems ground start TCP covers only digital interfaces. The protocol can handle T1 or E1 digital trunks, of signaling types FX (foreign exchange) or SA (special access). The trunk and signaling type is determined using the trunktype parameter.

If, in the past, you were using GST8 or GST9 protocols, you should now migrate to the Digital Ground Start (GDS) protocol. See Section 9.4 for more information about GDS parameters compatible with the GST protocols.

9.2 Capability Mask

With the NCC service, an application can call nccQueryCapability to determine the capabilities of a protocol (for example, overlapped sending and receiving, holding the call, and others). nccQueryCapability returns a capabilitymask.

For information about the capabilities supported for NMS CAS protocols with NCC call control, refer to Appendix A.

9.3 Signaling Overview

Although E1 Channel Associated Signaling (CAS) framing supports four signaling bits per direction, only two of them are used for Digital Ground Start line signaling. Thus the signaling channels supporting the Digital Ground Start line signaling protocol are referred to as A_f and B_f in the forward direction, and A_b and B_b, in the backward direction. The forward channel indicates the condition of the outbound switch equipment and reflects the condition of the calling party's line. The backward channel indicates the condition of the called party's line (the inbound equipment).

The other bits in either direction (the C and D bits) usually have fixed values. However, their values may change from network to network.

The following tables describe Digital Ground Start signaling in the two cases of FX and SA. Two tables are necessary, because the protocol changes depending on the side that started the call.

The following table illustrates the case in which the switch presents the call to the terminal equipment:

State	Outbound switch AfBf	Direction	Inbound terminal AbBb
Idle	11 (FX) 01 (SA)		01 (FX) 00 (SA)
Seizure	01 (FX) 11 (SA)		01 (FX) 00 (SA)
At this point, the incoming call is presented to the application. The application can answer or reject it. If the application answers it, after the specified number of rings the connected code is put on the line.
Ring on	00 (FX) 10 (SA)		01 (FX) 00 (SA)
Ring off	01 (FX) 11 (SA)		01 (FX) 00 (SA)
Answer - conversation state	01 (FX) 11 (SA)		11 (FX) 10 (SA)
If the inbound side application rejects the call instead, the TCP doesn't pick up the phone, and eventually the calling party will abandon the call.
In conversation state, if the switch side clears the call, a cleardown tone might be on the line. The terminal responds to this by hanging up the call.
Inbound disconnects first	01 (FX) 11 (SA)		01 (FX) 00 (SA)
Outbound disconnects	11 (FX) 01 (SA)		11 or 01 (FX) 10 or 00 (SA)
Idle	11 (FX) 01 (SA)		01 (FX) 00 (SA)

The following table illustrates the case in which the terminal equipment places the call:

State	Outbound terminal AfBf	Direction	Inbound switch AbBb
Idle	01 (FX) 00 (SA)		11 (FX) 01 (SA)
Seizure	00 (FX) 01 (SA)		11 (FX) 01 (SA)
Seizure acknowledge	00 (FX) 01 (SA)		01 (FX) 11 (SA)
Off hook	11 (FX) 10 (SA)		01 (FX) 11 (SA)
Proceed to send	11 (FX) 10 (SA)	dial tone	01 (FX) 11 (SA)
Here the outbound side starts to send the address information. This can be done by means of DTMF tones, or by decadic pulses. If the method is decadic pulses, the A-bit is switched off (pulse on) and on (pulse off) repeatedly to signal the digits. If the call is accepted, the network (or the PBX) plays ring on the line; otherwise it plays an appropriate call progress tone.
Answer - conversation state	11 (FX) 10 (SA)	voice	01 (FX) 11 (SA)
Inbound disconnects first	11 (FX) 10 (SA)		11 (FX) 01 (SA)
Outbound disconnects	01 (FX) 00 (SA)		11 or 01 (FX) 01 or 11 (SA)
Idle	01 (FX) 00 (SA)		11 (FX) 01 (SA)

9.4 Parameters

The Digital Ground Start TCP is programmed for operation within different countries and networks by a number of TCP-specific parameters. These are stored within the parameter category NCC.X.ADI_GDS.

Parameters in this category fall into two groups:

• Parameters that program TCP/host interaction, or that act on features not regulated or that can change from switch to switch within the same network. You can freely edit these parameters to suit your implementation.

• Parameters that are signaling-specific: changing their values invalidates approvals for the board, and may cause the board to malfunction. These parameters are described here for reference purposes only.
  Note: If you were previously using GST8 or GST9 protocols, migrate to the Digital Ground Start (GDS) protocol. For your convenience, a list of GST parameters (ADI field name) is compared to the GDS parameters in the parameter table.

9.4.1 Editable Parameters

The following table describes GDS parameters (within the parameter category NCC.X.ADI_GDS) that you may modify. Also listed are the equivalent ADI.GST parameters, to assist with migration from ADI to NCC.

NCC Field Name	ADI Field Name	Type/Units	Default	Description
nodialtonebehavior	optionflags (bits 0 and 1)	mask	0x0	Determines what to do if no dialtone is detected: 0 The TCP hangs up and abandons the call. 1 The TCP proceeds to dial anyway.
transfersupport	optionflags (bit 2)	mask	0x0	Selects whether PBX transfer is allowed: 0 Transfer commands are disabled. 1 Transfer commands are allowed.
CIDsupport	optionflags (bit 3)	mask	0x0	Indicates if caller ID is supported: 0 CID disabled. 1 CID enabled.
cleardowntone	optionflags (bit 4,5)	mask	0x0	If network side, tone to play as dial tone (if 0, don't play cleardown tone): 1 Play dial tone as cleardown tone. 2 Play busy tone as cleardown tone. 3 Play reorder (fast busy) as cleardown tone.
hangupsignal	signalingflags	mask	0x0	Flags that control the bit that signals hang up supervision. Note that cleardown tone will always be detected.: · Bit 0 (&0x1): Hang up supervision on the A bit (default). · Bit 1 (&0x2): Hang up supervision on the B bit.
trunktype	trunktype (bit 0)	mask	0x0	Determines the trunk type: 0 T1 1 E1
signalingtype	trunktype (bit 1)	mask	0x0	Determines the signaling type: 0 Foreign Exchange (FX) 1 Special Access (SA)

9.4.2 Non-editable Parameters

The following NCC.X.ADI_GDS parameters are country- or network-specific, and cannot be modified. Also listed are the equivalent ADI.GDS parameters, to assist with migration from ADI to NCC.

Caution:

Most of the parameters that follow are signaling-specific: changing their value will invalidate any approval certificate for the used board, and may cause the board to malfunction. These parameters are described here for reference purposes only.

NCC Field Name	ADI Field Name	Type/Units	Default	Description
bitqualtime	bitqualtime	ms	10	Qualification time for bit detector.
minringontime	minringontime	ms	100	Minimum duration of incoming ring.
maxringontime	maxringontime	ms	3000	Maximum duration of incoming ring.
maxringofftime	maxringofftime	ms	8000	Maximum duration of silence between rings.
ringstoincoming	numrings	count	0	Number of rings to detect for an incoming call: 0 1st ring begin 1 1st ring end n after n rings Note that if caller ID is enabled (optionflags bit 3 = 1) then the incoming call is reported after at least one ring.
dialtonewaittime	dialtonewaittime	ms	5000	For outgoing calls, the maximum time to wait for initial dial tone.
dialtonemintime	dialtonemintime	ms	1000	For outgoing calls, the minimum duration of non-precise dial tone required before dialing will begin. Set this to 0 to disable non-precise dial tone detection. (Precise dial tone detection is controlled by NCC.START parameters).
releaseguardtime	releaseguardtime	ms	1000	Minimum time between hang up and off hook.
CIDtype	CIDtype	integer	0	Type of caller ID protocol, if CID is enabled. 0 BellCore CID Protocol 1 NTT Japan CID Protocol 2 ETSI CID Protocol (V.23)
CIDmaxwaittime	CIDmaxwaittime	ms	0	Maximum time to wait for caller ID to arrive before concluding the caller has hung up (if CID is enabled).
CIDmaxalerttime	CIDalertmaxtime	ms	0	Maximum duration of an alert signal in caller ID protocol (if CID is enabled).
CIDminmarktime	CIDminmarktime	ms	100	Minimum duration of the "mark" signal of the caller ID protocol that is interpreted as such.
xferstring	xferstring	string[6]	"!;"	Prefix dial string for call transfer. The string is dialed before dialing the number, where: ! Flash hook ; (semicolon) Wait for precise dial tone.
connstring	connstring	string[6]	"!"	String for transfer back to the Connected state with the first call. It is dialed if a call transfer fails, where: ! Flash hook. *
connectbacktime	connectbacktime	ms	0x0	Time to wait after sending transfer back hookflash is the PBX was playing busy.
waitdialnodialtone	waitdialnodialtone	ms	500	Time to wait to dial if no dialtone detection is required.
ringsignalontime	ringsignalontime	ms	1000	Nominal ring-on time for network emulation.
ringsignalofftime	ringsignalofftime	ms	3000	Nominal ring-off time for network emulation.

The following parameters are served for internal NMS use:

• numdigits

• alarmsonqualtime

• alarmsonqualtime