static void idanswer(uint_fast8_t tx)
{
    static const prog_char fmt [] =
        "ID"            // 2 characters - information code
        "%03u"        // 3 characters - model
        ";";                // 1 char - line terminator
    // answer mode
    const uint_fast8_t len = local_snprintf_P(cat_ask_buffer, CAT_ASKBUFF_SIZE, fmt,
        (unsigned int) 21    // 021 - code of TS-590S model
        );
    cat_answer(cat_ask_buffer, len);
}