Types of Computer Modem

This presentation includes the function of the modem, types of modem

1. Modem Introduction: A modem [ Modulator -Demodulator ] is a device. Data communication means transmitting digital information form one computer to other computers through the comunication channels . Communicate equipment used for long distance data transfer through telephone lines. A pair of modems are needed to communication

2. Mod e m

3. Cont . , Com m un i cat i on bet w e e n co m pute r s through the existing telephone cables.

4. Structure of data communication through modem Analog data Digital data

5. Working principle The d i g ital converted dat a from the c o m pute r is into analog data by t h e over t h e m o de m an d ar e tran s m i tted telephone line.

6. Cont . , The analog data received from the telephone line is converted to digital by the modem and is given to the computer.

7. This unit receives serial data and gives it to the modulator . It receives demodulated data from the demodulator and gives it to the modem processor. This interface is used to connect computer and modem through serial port using standard RS232C used in external modem for bits conversion.

8. Modulator This unit is used to convert the digital data from computer into analog data. This process is called modulation. This is done by adding a carrier signal to the digital signal.

9. Cont . , 1 1 0 1 1 1 1 Amplitude modulation

10. Demodula t or This unit is used to convert the analog data from telephone system into digital data. This is done by eliminating the carrier signal from analog signal. 1 1 0 1 1 1 0 1 D emodulat i on

11. Pho n e interface Connect modem with the phone socket. Dial the umber for making communication. Detect the incoming ring signals. Co nn ect spe a ker information, ring for to n e, giving data vo i ce to n e, engaged tone etc.,

12. Pho n e Socket

13. T ype s o f modems Two types of modem. External modem Internal modem

14. External modem

15. External modem Ex t ernal m o de m i s s e p arat e dev i ce a nd is kept outside the computer. A 9 pin (DB9) or 25 pin serial cable connects the PC serial port to the modem. Thus CPU need not be opened during modem installation. External modems avoid hardware conflicts such as (conflict of I/O address lines and that of interrupt lines) the external modem setup is faster and easier than internal modems .

16. Internal modem In t ernal m o de m i s a par t o f t h e co m puter and is connected inside the system.

17. Internal modem Internal modem that plugs directly into PCI or ISA expansion slot. Peripheral Component Interconnect Industry Standard Architecture modulator converts digital data from computer into analog signal which is transmitted through RJ-11 jack . (Registered Jack) On receiver side receive the analog signal and pass them to demodulator it converts signal and sends to UART. ( Universal Asynchronous Receiver/Transmitter)

18. Internal modem It then converts serial bit data into parallel byte Co n trol l er i s used to manage o v erall operation of modem Non-volatile RAM (NVRAM) it stores modem parameters.

19. Installing Switch off the computer and connect the modem. The computer is switched on , it detect the modem and displays new hardware found dialog box. Insert the installation CD. After completing installation close the windows and restart the computer. Test the modem by the phone dialer option given in the accessories.