Ok , this may be another stupid question from my site any ways here goes:-

Today i purchased a made in china telephony related device with following features:-

1) One External Telephone Line can be connected with this device , 1 input.

2) two telephone sets can be connected as extensions so this become a 1+2 PBX with limited features...

3) we can do programming of the device using the normal telephone set for setting up different features as explained in its mannual..

my first question:-

1) Is programming a device using a telephone set (i.e. an external device) involves learning flash memory and also to save the programming while power goes out and comes again ..is it flash memory or something esle that i need to learn?

2) while going through its parts i found that the manufacturer has used a 20 Pins 89c2051 controller on which 24PC, 9943 is also written , also there are 2 12 Mhz crsytals. Is using 20 Pins controller is more efficient , economical or size is the factor , what you think? is the same coding is used for this controller also or something else and what abt pin configruation?

other components include:
Any idea about the purpose of these ICs, i am searching for these but just asking your guess:

906ATKG3

24WCCO2R

LTDF06M

HT9170

and then 3 1 Ampere , 125 VAC , 1 A 30 VDC relays are used....

for those who know about pbx design ..here there is no SLIC then who the Trip and Ring connection occurs...is relay playing the main role?