Why is there a signal when you dial *228 when there is no signal in the telecom? This mobile phone does not support telecommunications.

Depending on the mobile phone network standard, the telecom card can't be used without hardware support.

First, the network standard of mobile network:

1, mobile 4G: mobile TD-LTE；; ;

2. Mobile 3G: TD-SCDMA;

3. Mobile 2G: GSM.

Second, the network standard of telecommunication network:

1, telecom 4G: telecom TD-LTE, telecom FDD-LTE；;

2. Telecom 3G:CDMA 2000；;

3. Telecom 2G: CDMA.

Three, China Unicom network standards:

1, Unicom 4G: Unicom TD-LTE, Unicom FDD-LTE；; ;

2. Unicom 3G:WCDMA；;

3. Unicom 2g: GSM.