C++- getting error while try to use template

I am new to c++, and reying to use templates. I have a function which can get some classes.

template <class T>
response_t send_sequence_to_device(map<const string_t, T*> msg2device_p,vector<response_t>& result_list, ushort num_attempts=SEND_NUM_ATTEMPTS);

I get the following errors: error: 'T' was not declared in this scope error: template argument 2 is invalid error: template argument 4 is invalid