Outgoing Call Clause Samples

Outgoing Call. Modem pool dialling with outgoing calls is usually only applied on trunk lines which support DDO. If a modem in the modem-pool is idle, all signals between the MLU and the modem are in the off-condition. If a party (internal) initiates a call request to a destination (trunk access code to a destination via an analogue trunk line with CV), the compatibility check is used to find out that a modem of a specific type must be used for that trunk line. Now a free circuit on a MLU with the correct modem type is seized. For an outgoing call, first the dial information is transferred over the trunk line in the applicable signalling type (bundle dependent!). The V.25 Automatic Calling Unit of the modem is not used. Two data paths are established through the switching network: - From the destination party to the MLU: The V.24 user data is incorporated in a 2B+D 64 kbps signal by a SOPHO-SET, SOPHO- ▇▇▇ or ▇▇▇ and transferred to the MLU circuit via the DLC-circuit and the switching network. The V.24 user data is retrieved from the 64 kbps signal and sent to the modem. - From the MLU to the ATU circuit: After modulation the analogue modem signal is digitised and sent in a 64 kbps signal to the ATU circuit. Here the modulated user information is reconstructed back to analogue and sent over the trunk line. For full duplex data communication, the reversed path must also be established through the switching network. Now call processing starts waiting for the call to be answered. The call establishment is guarded by timers. When the call is answered by the destination party, the pool-modem is activated: - CT108.1 (CDSL) forces the modem on-line; - CT111 (DSRS) is sent to the modem to indicate if the high or the low speed must be used- depending on the projecting of the MLU-circuit; - CT126 (STF) is set in the off-condition to indicate the modem must send in the low- frequency band and receive in the high-frequency band (calling mode); - The modem returns the signal CT107 (DSR) to the MLU circuit to indicate the modem is ready for operation; - If the V.25 tone sequence is used, either the modem or the MLU circuit sends calling tone and starts waiting for the answer tone. If the answering tone is detected by the modem or the MLU circuit, the calling tone is stopped. If the V.25 tone sequence is not used, this step is skipped; - The MLU circuit forces circuit CT105 (RTS) to on; - The modem starts waiting for the backward 2400 Hz carrier. If this carrier is detected the modem k...