User talk:Kataneh

CTM (Cellular Text Telephony Modem)
As per 3GPP standard of TS 26.226, CTM allows reliable transmission of a text telephone conversation alternating with a speech conversation through the existing speech communication paths in cellular mobile phone systems.

This technology allows the reliable transmission of text via the speech channel of cellular phone systems or PSTN networks.

A traditional text telephone modulation technique also exists that was designed years ago for PSTN lines. Traditional technique is more reliable. The reason is that mobile networks and devices are optimized for voice. Moreover, cellular phones use speech coding in order to compress the signal. As a result of coding modem signals might get corrupted. As a result of speech-optimized networks character error rate (CER) might happen in poor channel conditions.

Reference: ARIB STD-T63-26.226 V5.0.0; Cellular Text Telephone Modem; General Description (Release 5)