public final void setTelno(final byte length, final byte[] packedDigits) {
        if (length > MAX_TELNO_LENGTH
                || length < 0
                || packedDigits.length < ((length + 1) / 2)) {
            throw new IllegalArgumentException();
        }

        mTelno = new byte[TELNO_BYTES_LENGTH];
        mTelno[1] = length;
        for (int i = 0; i < packedDigits.length && i < ((length + 1) / 2);
        i++) {
            mTelno[i + 2] = packedDigits[i];
        }
    }