... ; caller tracing; 2. Automatic CONTACT ID,4+2 EXPRESS,4/2,4 /1 and 3/1 policing call format ... identification; 3. Convenient installation and setup 4. Lightning-proof 5. Police call buzz reminding 6. ... display 15. Self-definition of 3/1, 4/1 and 4/2 report codes 16. Amplifiable e-map 17 ... (communication protocol): CONTACT ID,DTMF 4+2EXPRESS, 3/1,4/1 and 4/2 pulse(10-40pps),caller id ...