What is difference between M and MP?

For the CDP-TX-07M, CDP-RX-07M, frequency setting is performed with the 2-bit solder Jumper.
For the CDP-TX-07MP, CDP-RX-07MP have 2-pin (S1 and S2) connectors for frequency setting, making it possible to set the channels externally. Click here for more details or refer to the application note.