  function transfer(address _to, uint256 _value) public returns (bool) {
    require(active);
    require(_to != address(0));
    require(_to != msg.sender);
    require(_value <= balances[msg.sender]);
    uint256 bal = balances[_to] + _value;
    require(bal >= balances[_to]);
    balances[msg.sender] = balances[msg.sender] - _value;
    balances[_to] = bal;
    emit Transfer(msg.sender, _to, _value);
    return true;
  }