# EUC country-specific signaling

The EUC TCP implements the national CAS specifications of three European countries: Italy, Sweden, and the Netherlands. These countries define protocols that use two bits line signaling and DTMF digit spill register signaling, and are similar enough to be implemented by the same trunk control program.

Although E1 channel associated signaling (CAS) framing supports 4 signaling bits per direction, only 2 of them are used for the protocols implemented by the EUC TCP. Thus the signaling channels supporting the line signaling of these protocols are referred to as Af and Bf in the forward direction, and Ab and Bb, 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 C and D bits never change. Their value is 0 and 1 respectively.

The following country-specific tables describe the line signaling for a typical call:

- EUC signaling for Italy (Norma CEI 103-1/7)

- EUC signaling for Sweden (P7/P8)

- EUC signaling for the Netherlands (ALS70D)