Common use of Outgoing Call Clause in Contracts

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 knows the opposite party is on-line. The circuit CT109 (DCD) indicates to the DTE (MLU) that the DTE must also be ready to accept data. The modem now starts transmitting the 1200 Hz carrier in the forward channel and returns CT106 (RFS) to the DTE to indicate the DTE may starts sending. The connection between the remote party and the local party is established.

Outgoing Call. Modem pool dialling For an outgoing call over a leased line, the procedure is the same as the seizure of a free trunk line when making an outgoing -voice- call. Therefore the MLU-circuits with outgoing calls the modems connected, are assigned a line number and related to a bundle, route and destination. When an internal data party wants to have access to the external data party, only the trunk access code to the destination is usually only applied enough (CV connection allowance: allowed) to seize a free line (including modem) to the external data party. 1. The modem returns the signal CT107 to indicate that the modem is ready for operation. Guarding of the line: In some cases the remote data party offers a constant carrier on trunk lines which support DDOthe line. In this case the signal CT109 from the modem indicates that the carrier is being received. If this carrier is not present, it may indicate a modem problem with the line and the MLU circuit is set into the ABL-FAIL condition. The guarding of the line can be enabled or disabled in the modem-pool projecting data. For more information: see Projecting aspects. If the send and receive frequency of the modem is idle, all signals between controlled by the MLU and by signal CT126 (STF), the constant carrier can only be in the high frequency band. If the modem are is idle the signal CT126 is in the off-condition. The modem is set in the calling mode and only detects the carrier in the high-frequency band. If the send and receive frequency is controlled by the modem itself (switchess and/or straps) the constant carrier can be in the high (modem in calling mode) or in the low (modem in answering mode) channel. If a party (internal) initiates a call request to a destination (trunk access code to a destination via an analogue trunk line with CVcode), the compatibility check is used to find out that a modem of a specific type must be used for that trunk lineallows the connection. Now a free circuit on a MLU with in the correct modem type route is seized. For an outgoing call, first the dial information One data path 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 calling 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 The outgoing route option `direct switch through' must be yes. As no answer signal can be received over this `trunk line' (not an ATU-circuit), call processing starts waiting does not wait for an answer signal from the call to be answered`trunk line' but immediately establishes the transparent connection between the remote and the local modem. The call establishment is guarded by timers. When rest of the call is answered connection set-up must be performed by the destination party, MLU and the pool-modem is activatedmodem: - 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-MLU circuit; - CT126 (STF) is set in sent to the off-condition modem to indicate if the modem must receive in the high frequency band and send in the low- frequency band and receive in the high-low frequency band (calling mode); - The modem returns ) or receive in the signal CT107 low frequency band and send in the high frequency band (DSR) to answering mode)-depending on 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 projecting of 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 knows the opposite party is on-line. The circuit CT109 (DCD) indicates to the DTE (MLU) that the DTE must also be ready to accept data. The modem now starts transmitting the 1200 Hz carrier in the forward channel and returns CT106 (RFS) to the DTE to indicate the DTE may starts sending. The connection between the remote party and the local party is established.