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Chapter 12

Digital Ground Start Protocol

12.1 Introduction

12.2 Signaling Overview

12.3 Parameters

12.1 Introduction

This chapter describes the digital Ground Start signaling protocols and TCP parameters.
Although ground start protocols exist in both analog and digital variations, Natural MicroSystems ground start protocols cover only digital interfaces.
The digital trunks are usually T1. The protocol comes in two flavors: FX (foreign exchange), and SA (special access). GST-FX is covered by the GST8 TCP, GST-SA by the GST9 TCP.

12.2 Signaling Overview

The following tables describe digital ground start signaling in the two cases of GST-FX and GST-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 Line Inbound terminal AbBb Idle 11 (GST-FX) 01 (GST-SA) \xdf 01 (GST-FX) 00 (GST-SA) Seizure 01 (GST-FX) 11 (GST-SA) 01 (GST-FX) 00 (GST-SA) At this point, the incoming call is presented to the application. The application can answer or reject it. If it answers it, after the specified number of rings the connected code is put on the line. Ring on 00 (GST-FX) 10 (GST-SA) 01 (GST-FX) 00 (GST-SA) Ring off 01 (GST-FX) 11 (GST-SA) 01 (GST-FX) 00 (GST-SA) Answer - conversation state 01 (GST-FX) 11 (GST-SA) \xdf 11 (GST-FX) 10 (GST-SA) If the inbound side application rejects the call instead, the GST8/9 TCPs don'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 (GST-FX) 11 (GST-SA) \xdf 01 (GST-FX) 00 (GST-SA) Outbound disconnects 11 (GST-FX) 01 (GST-SA) 11 or 01 (GST-FX) 10 or 00 (GST-SA) Idle 11 (GST-FX) 01 (GST-SA) \xdf 01 (GST-FX) 00 (GST-SA)
The following table illustrates the case in which the terminal equipment places the call: State Outbound terminal AfBf Line Inbound switch AbBb Idle 01 (GST-FX) 00 (GST-SA) \xdf 11 (GST-FX) 01 (GST-SA) Seizure 00 (GST-FX) 01 (GST-SA) 11 (GST-FX) 01 (GST-SA) Seizure acknowledge 00 (GST-FX) 01 (GST-SA) \xdf 01 (GST-FX) 11 (GST-SA) Off hook 11 (GST-FX) 10 (GST-SA) 01 (GST-FX) 11 (GST-SA) Proceed to send 11 (GST-FX) 10 (GST-SA) \xdf dial tone 01 (GST-FX) 11 (GST-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 any appropriate call progress tone. Answer - conversation state 11 (GST-FX) 10 (GST-SA) \xdf voice 01 (GST-FX) 11 (GST-SA) Inbound disconnects first 11 (GST-FX) 10 (GST-SA) \xdf 11 (GST-FX) 01 (GST-SA) Outbound disconnects 01 (GST-FX) 00 (GST-SA) 11 or 01 (GST-FX) 01 or 11 (GST-SA) Idle 01 (GST-FX) 00 (GST-SA) \xdf 11 (GST-FX) 01 (GST-SA)

State	Outbound switch AfBf	Line	Inbound terminal AbBb
Idle	11 (GST-FX) 01 (GST-SA)	\xdf	01 (GST-FX) 00 (GST-SA)
Seizure	01 (GST-FX) 11 (GST-SA)		01 (GST-FX) 00 (GST-SA)
At this point, the incoming call is presented to the application. The application can answer or reject it. If it answers it, after the specified number of rings the connected code is put on the line.
Ring on	00 (GST-FX) 10 (GST-SA)		01 (GST-FX) 00 (GST-SA)
Ring off	01 (GST-FX) 11 (GST-SA)		01 (GST-FX) 00 (GST-SA)
Answer - conversation state	01 (GST-FX) 11 (GST-SA)	\xdf	11 (GST-FX) 10 (GST-SA)
If the inbound side application rejects the call instead, the GST8/9 TCPs don'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 (GST-FX) 11 (GST-SA)	\xdf	01 (GST-FX) 00 (GST-SA)
Outbound disconnects	11 (GST-FX) 01 (GST-SA)		11 or 01 (GST-FX) 10 or 00 (GST-SA)
Idle	11 (GST-FX) 01 (GST-SA)	\xdf	01 (GST-FX) 00 (GST-SA)

State	Outbound terminal AfBf	Line	Inbound switch AbBb
Idle	01 (GST-FX) 00 (GST-SA)	\xdf	11 (GST-FX) 01 (GST-SA)
Seizure	00 (GST-FX) 01 (GST-SA)		11 (GST-FX) 01 (GST-SA)
Seizure acknowledge	00 (GST-FX) 01 (GST-SA)	\xdf	01 (GST-FX) 11 (GST-SA)
Off hook	11 (GST-FX) 10 (GST-SA)		01 (GST-FX) 11 (GST-SA)
Proceed to send	11 (GST-FX) 10 (GST-SA)	\xdf dial tone	01 (GST-FX) 11 (GST-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 any appropriate call progress tone.
Answer - conversation state	11 (GST-FX) 10 (GST-SA)	\xdf voice	01 (GST-FX) 11 (GST-SA)
Inbound disconnects first	11 (GST-FX) 10 (GST-SA)	\xdf	11 (GST-FX) 01 (GST-SA)
Outbound disconnects	01 (GST-FX) 00 (GST-SA)		11 or 01 (GST-FX) 01 or 11 (GST-SA)
Idle	01 (GST-FX) 00 (GST-SA)	\xdf	11 (GST-FX) 01 (GST-SA)

12.3 Parameters

The parameters that program the GST8 and GST9 TCPs belong to the ADI.GST category. The following table describes the relevant ADI.GST parameters. Field Name Type/Units Default Description cidsupport n/a 0 Indicates if caller ID is supported: Value Definition 0 CID disabled 1 CID enabled 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 ADISTART parameters). dialtonewaittime ms 5000 For outgoing calls, the maximum time to wait for initial dial tone. interringmaxtime ms 8000 The maximum length of an incoming ring period (on time + off time) that can elapse before the call is considered to be abandoned. nodialtoneaction n/a 0 Selects what to do if no dial tone detected: Value Definition 0 Hang up and abandon the call 1 Proceed to dial anyway 2 Generate an incoming call event numrings count 0 Number of rings to detect for an incoming call: Value Definition 0 1st ring begin 1 1st ring end n after n rings Note that if caller ID is enabled (cidsupport = 1) then the incoming call is reported after at least one ring. qualloopoff ms 10 Minimum duration of loop current interruption before a hang-up will be recognized. qualringoff ms 100 For voltage-sensitive ring detection, the minimum duration of loss of detected voltage to be recognized as the end of a ringing signal. qualringon ms 6 For voltage-sensitive ring detection, the minimum duration of detected voltage to be recognized as the start of a ringing signal. releaseguardtime ms 1000 Minimum time between hang up & off hook. ringsigmintime ms 100 Inbound minimum ring time (+qual). ringsigmaxtime ms 3000 Inbound maximum ring time (+qual). xfersupport n/a 1 Flag to select whether PBX transfer is allowed. Value Definition 0 Transfer commands are disabled 1 Transfer commands are allowed

Field Name	Type/Units	Default	Description
`cidsupport`	n/a	0	Indicates if caller ID is supported: Value Definition 0 CID disabled 1 CID enabled
`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 `ADISTART` parameters).
`dialtonewaittime`	ms	5000	For outgoing calls, the maximum time to wait for initial dial tone.
`interringmaxtime`	ms	8000	The maximum length of an incoming ring period (on time + off time) that can elapse before the call is considered to be abandoned.
`nodialtoneaction`	n/a	0	Selects what to do if no dial tone detected: Value Definition 0 Hang up and abandon the call 1 Proceed to dial anyway 2 Generate an incoming call event
`numrings`	count	0	Number of rings to detect for an incoming call: Value Definition 0 1st ring begin 1 1st ring end n after n rings Note that if caller ID is enabled (`cidsupport` = 1) then the incoming call is reported after at least one ring.
`qualloopoff`	ms	10	Minimum duration of loop current interruption before a hang-up will be recognized.
`qualringoff`	ms	100	For voltage-sensitive ring detection, the minimum duration of loss of detected voltage to be recognized as the end of a ringing signal.
`qualringon`	ms	6	For voltage-sensitive ring detection, the minimum duration of detected voltage to be recognized as the start of a ringing signal.
`releaseguardtime`	ms	1000	Minimum time between hang up & off hook.
`ringsigmintime`	ms	100	Inbound minimum ring time (+qual).
`ringsigmaxtime`	ms	3000	Inbound maximum ring time (+qual).
`xfersupport`	n/a	1	Flag to select whether PBX transfer is allowed. Value Definition 0 Transfer commands are disabled 1 Transfer commands are allowed

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