EUC signaling for the Netherlands (ALS70D)

ALS70D, the Dutch National CAS protocol, is asymmetrical, meaning that the terminal equipment sends and receives different signals to perform call setup with respect to the near-end switch. Thus, two signaling tables are necessary to specify the protocol, one for the TCP placing calls (outbound), and one for the TCP receiving calls (inbound).

This topic describes how signaling is carried out by the:

Signaling carried out by the outbound TCP

The following table shows signaling states associated with the outbound TCP when using the EUC TCP for the Netherlands:

State

Outbound AfBf (TCP)

Direction

Inbound AbBb (Network)

Idle

10

10

Seizure

00

10

The normal behavior after the outbound TCP signals seizure is the detection of a seizure acknowledged. However, call collision can occur, and the TCP can receive a seizure from the network as well. If the seizure from the network comes 200 ms from the original seizure, then the outbound TCP must send seizure acknowledged and receive a call. It then behaves as shown by the table, describing the inbound TCP behavior.

Seizure acknowledged

00

11

The inbound network side starts playing a dial tone on the voice channel, meaning that in-band (DTMF detector) resources are available to receive the address information.

Once it has detected the dial tone, the outbound side starts to send the address information using DTMF tones or pulse dial. If the method is pulse dial, the Bf bit is switched on (pulse on) and off (pulse off) repeatedly to signal each digit.

Register signaling: digit spill

DTMF

11

Register signaling: pulse dial

01 pulse on

11

 

00 pulse off

11

If the call is accepted, the inbound side plays a ring tone on the line and then flips the Ab bit to signal 01. Otherwise, it flips the Bb bit to signal 10 (idle).

Ringing

00

11

Answer - conversation state

00

01

The outbound protocol can receive billing pulses to signal that a unit of cost was billed to the call. In this case, the answer pattern (AB = 01) from inbound temporarily changes to AB = 00.

Answer - conversation state

00

01

Billing pulses

00

00

Answer - conversation state

00

01

Depending on which side hangs up the call first, a clear forward signal or a clear back signal is generated, followed by a clear forward. Idle follows.

Clear back

00

11

Clear forward

10

01 (or 11)

Idle

10

10


Signaling carried out by the inbound TCP

The following table shows signaling states associated with the inbound TCP when using the EUC TCP for the Netherlands:

State

Outbound AfBf (Network)

Direction

Inbound AbBb (TCP)

Idle

10

10

Seizure

00

10

Seizure acknowledged

00

11

The seizure acknowledged line state for the inbound TCP lasts for a certain time period. This time period is set to 100 ms in the TCP. After that, a ready to receive bit transition is sent to signal the network that the TCP is ready to receive the address information. This signal means that the resource dedicated to detect DTMF tones has been allocated.

Ready to receive

00

01

Once it detects the ready to receive signal, the outbound side starts to send the address information using DTMF tones or pulse dial. If the method is pulse dial, the Bf bit is switched on (pulse on) and off (pulse off) repeatedly to signal each digit.

Register signaling: digit spill

DTMF

01

Register signaling: pulse dial

01 pulse on

01

 

00 pulse off

01

When all the digits have been received, the inbound side flips the Ab bit to signal that it has enough information. This state is maintained for at least 300 ms.

Number received

00

11

If the call is accepted, the inbound side plays a ring tone on the line and then flips the Ab bit to signal AB = 01. Otherwise, it plays busy and flips the Bb bit to signal AB = 10 (idle).

Ringing

00

11

Answer - conversation state

00

01

Depending on which side hangs up the call first, a clear forward signal or a clear back signal is generated, followed by a clear forward. Idle follows.

Clear back

00

11

Clear forward

10

01 (or 11)

Idle

10

10