> 3.1.3 | Dependencies between Multiplex Channels and Restrictions of Use

> When using the following functions, be aware of possible dependencies between the different channels. One way of avoiding problems may be to dedicate certain commands/features to one of the channels or to assure that the application avoids conflicts.

> • | Call control: A voice call can be initiated, answered or ended on each channel. Data and fax calls shall be made on channel 1 only. See AT commands like ATD, ATA or ATH. ATH terminates each voice, circuit switched data or fax call regardless on which logical channel ATH was executed. In the case of GPRS, ATH is effective only on the channel where executed. For details see [2]. Example: An ongoing fax call has been established on channel 1. When answering an incoming voice call on channel 2 or 3 and terminating it, the held fax call will be ended as well.

> • | Phonebook access: If you wish to write the same phonebook entry on two different channels at the same time, please note that the last entry will be stored permanently. All other data will be deleted.

> • | SMS read, write and delete.

> • | Time settings: Though the AT commands AT+CALA and AT+CCLK can be used on either channel, the same time setting applies to all three channels. It is only the alarm message <text> which may be specific to each channel. The URC "+CALA" will be issued only on the channel where the last alarm setting was made. For details see [2].

> • | Device locks set with AT+CLCK.

> • | SIM card access.

> • | RF settings.

> • | Note specific to product families AC4x, MC3x, TC35ix, MC5x, XT5x:

> Open at least channel 1. Otherwise, if only channel 2 or 3 is opened, data associated to the closed virtual channel(s) may be output as unframed data.
> Example: Assume that channel 1 and 2 are closed, a voice call is made on channel 3 and the remote subscriber hangs up. The "NO CARRIER" result code which normally appears on all 3 channels cannot be sent to channel 1 and 2, resulting in unframed data that cannot be allocated to a channel. Yet, there is no loss of data because the unframed characters are only additional data sent between the framed data of the opened channel.