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Monday, January 21, 2013

Chinese electronics recycle fun or what's inside gsm to landline phone terminal

Here we go. I have a simple gsm terminal for landline phones, so I can call from regular analog phones through gsm network. I'm using it in low signal area with external antenna.
So one day I decided to look what's inside of it. I was thinking there would be some kind of gsm modem inside and analog support electronics etc. But found some interesting stuff.
Here how this thing looks, nothing important just grey box with gold antenna output sma socket.

Now let's take a look inside:

Yes, it is a gsm cell phone pcb inside! With phone battery for backup power. This thing is powered by nuvoTon W78E052DDG mcu. Which has 80C51(52) core. Never heared of them yet, but they make Cortex-M0 mcu and other ARMs too. I guess it is connected to the phones serial port.

Wires soldered directly to pcb connector.

Looks like Nokia or SE connector to me.

Wires soldered directly to phone external connector.
Phone pcb screwed to terminal housing posts, so this housing is made for this particular phone pcb on purporse. It means some kind of cellphones recycling =) Chips on phone pcb has date codes leading to 1999.

Wires soldered to the phones sim socket leads to a new sim socket on bottom side of terminal main pcb.

Some unknown chip under pcb.

Here must be some know-how, otherwise I don't know why they sand those chips markings.

LCD board glued in place =) This LCD board is connected through serial data line, may easily be reused. There is a black blob lcd controller on pcb.

LCD itself actually has a good contrast.

I had used a cell phone as wireless terminal to send sms alerts. But I never though this would be used in actual manufacturing =)

Update: as requested I pictured main pcb bottom side: