> 18.17 | AT^SNFTTY Signal TTY/CTM audio mode capability

> TC65 offers basic support for equipment using the CTM standard (Cellular Text Telephone Modems). The benefit of CTM is that text characters typed on a TTY device (Text Telephone Type-writer) can be transformed into special audio burst signals for reliable transmission via the existing speech channels of a cellular phone system.
> If CTM mode is activated, the ME will set the necessary bearer capability bit on outgoing (mobile originated) calls and incoming calls with this bearer capability bit set are accepted. The TE needs to decode the special audio burst signals.
> If CTM mode is disabled, the ME will clear the bearer capability bit on mobile originated calls and incoming calls with the bearer capability bit set are rejected because the TC65 expects that CTM coded speech data cannot be decoded by the TE.
> Designed to set the module's speech system into CTM mode, the AT^SNFTTY command allows a CTM device to be connected to one of the three audio interfaces of TC65. Traditional TTY devices that do not incorporate CTM functionality can be connected through an external TTY-to-CTM adapter.
> Related documents: Refer to the relevant standards, such as 3GPP TS 26.226 (ETSI TS 126 226) and 3GPP TS 23.228 (ETSI TS 123 226). 3GPP documentation can be retrieved, for example, from http://www.3gpp.org/specs/specs.htm. Application Note 22 "Using TTY/CTM equipment" supplies information needed to connect TTY/CTM equipment to the TC65.
> Requirements for using TTY/CTM features:

> • | TTY/CTM functionality requires audio mode 5 or 6 with all audio parameters set to their factory default. Before activating TTY/CTM mode, first enter the AT^SNFS command to select the audio mode, then use AT^SNFI and AT^SNFO to restore the default values. Alternatively, factory defaults of audio parameters can easily be set with AT^SNFD. Keep in mind that the TTY/CTM mode is non-volatile. The audio mode, however, is volatile (power-up default is audio mode 1) unless stored to the user defined profile with AT^SNFW. Therefore, if restarted while in TTY/CTM mode the ME may need to be reconfigured for audio mode 5 or 6 before the TTY/CTM mode is selectable again after the reboot.

> • | Depending on which audio interface the CTM device is connected to, select the appropriate settings via AT^SAIC.

> Syntax

> Test Command AT^SNFTTY=?
> Response(s)
> ^SNFTTY: (list of supported <audioState>s)
> OK

> Read Command AT^SNFTTY?
> Response(s)
> ^SNFTTY: <audioState>
> OK

> Write Command AT^SNFTTY=<audioState>
> Response(s)
> OK
> ERROR
> +CME ERROR: <err>

> Reference(s) |  | PIN |  | ASC0 | ASC1 | USB | MUX1 | MUX2 | MUX3 |  |  | Charge | Q | Last
> SIEMENS |  | - |  | + | + | + | + | + | + |  |  | - | - | -

> Parameter Description

> <audioState>(num)

> This setting is non-volatile.
> 0
> Audio path is in normal speech mode.
> 1
> Audio path is in TTY/CTM mode.