CAS R1 LOOPSTART USER

Revision as of 11:03, 8 August 2013

Loopstart is a CAS R1 variant.

Loopstart is an asymmetrical variant where a FXS (or "user") and FXO (or "network") sides must be face to face.

Current page describes the Loopstart FXS variant, see the following page for documentation about Loopstart FXO variant.

You can find general documentation about CASR1 scripts in Toolpack in the following page:CASr1_scripting.

Overview

In the Loopstart variant, FAX side is sending CAS bit A, used to indicate if user's phone is "on hook" or "off hook", while it receives CAS bit B from network side to indicate when it's required to make the user's phone ring.

Initial CAS bits values:

• Bit A (from user) is 1 ("on hook")
• Bit B (from network) is 1 ("ringer off")

Summary of the Loopstart call flow:

• Call establishment:
  • User calling:
    • FXS side set CAS bit A to 1, indicating that the phone is "off hook"
    • FXS side wait for a dial tone
    • FXS side dials the DNIS (called number)
    • User should hear ring tone, then remote party
  • Network calling:
    • FXS side detects bit B changes to 0, and makes the phone ring
    • FXS side detects bit B toggles, and makes the phone ringer "on" and "off" accordingly
    • FXS side set CAS bit A to 1, indicating that the phone is "off hook"
• Call termination (user side only, network has no way to terminate the call):
  • FXS side set CAS bit A to 0, indicating that user's phone is "on hook"

Note: There is no way, in Loopstart variant, for network side to report when the call is answered, or terminated. The caller considers the call answered when the ring tone ends and when someone starts talking. The caller considers the call terminated when the conversation is over, or when it no more hears the remote party.

Configuration

Choosing tone type

With CAS R1, DNIS (called number) can be sent using either DTMF or MFR1 tones.

To specify the type of tones to use, use the following constant:

TONE_USE_DTMF			= 1

Transmission of DNIS

Optionnally, a suffix and/or prefix may be added to the DNIS (called number) that Toolpack sends toward the FXO side:

	DNIS = {
		prefix = "",
		suffix = "",
	},

Note that prefix and suffix are rarely used in this variant.

Also note that detection of DNIS does not need to be configured in the FXS variant, because a call from FXO to FXS side does not provide any DNIS, and thus FXS side never has to detect a DNIS.

Detailed information about the Loopstart FXS script and state machines

For more detailed information about how this script is implemented (various states, and options), please refer to the "loopstart_fxs.lua" script provided with Toolpack.