# EUC register signaling

In general the protocols supported by the EUC TCPs use either in-band DTMF tones or out-of-band decadic pulses to transfer register signaling information.

The Italian and Dutch protocols only transfer DID (direct inward dialing - the called address) information. To do this the outbound side sends either a stream of DTMF tones or a sequence of decadic pulses to the inbound side, then considers the dialing done and waits for some confirmation from the inbound side. This register signaling technique, in which the outbound side has no acknowledgment from the inbound side until the dialing is finished, is called digit spill.

The Swedish P8 protocol (setting up calls from the network to a CPE) can transfer other kinds of information. An incoming call with P8 can convey the following:

- ANI digits (caller ID);

- The last redirecting number (if the call was redirected from another terminal); or

- Both of the above.

To do this, the protocol still uses a DTMF digit spill, but with special codes and separators that delimit the different fields.

The syntax is the following:

[Ac 1 c 2 c 3 c 4 c 5Dt 1...t n[Dt 1...t n]C]d 1...d n

Where:

- The A, C, and D characters must be taken literally (A=DTMF A)

- c n is a DTMF tone used as a code element between the A and D digits

- t n is a tone representing information about the call

- C represents the end of the call information part of the digit spill

- d n is a DID digit.

A maximum of two D digits (separators) can be present, depending on the code that follows the A digit. If the first DTMF tone received is not A, only DID digits are present.

The following table describes the valid codes:

Code | Description
00000 | Only ANI information is available (one Dt 1...t n sequence)
00030 | Only last forwarding number available (one Dt 1...t n sequence)
00031 | ANI and last forwarding number available (two Dt 1...t n sequences, first ANI and second last redirecting number)