Diagnostics

Two stickers inside the phone reveal in built diagnostics

Enter test mode by exposing the LDR on circuit board to light then go off hook ?

where you see FOC in instructions press the "follow on call" button

FOC 15 - If the phone is in 999 calls only mode FOC 15 will tell you why.

In this video we have 3 Faults

9 ????

7 cash container full

1 RAM needs to be programmed

Status check FOC 16 -

This test looks at the connection back to the exchange

Test Call FOC 26

In this video after FOC 26 is entered, the phone is ready to accept coins, 2 coins are inserted the credit builds up, then the money is refunded.

From Chris:

Test Call, 26. Yes, it just makes the state as it would be for a normal call, but it does so *bypassing all the checks* the phone normally does when starting up. So even if the phone is in 999 Calls Only, a test call will force it into normal call mode regardless of whatever issue forced it to 999 Calls Only, making it possible to make a call even if the configuration is totally lost or there is some other problem such as a broken handset loop. You still have to put money in, even if the first byte, the minimum fee, is zero. If it is zero, which, to be fair, may well not be the case in many loss of memory incidents, then, with some money in, it will allow normal dialling. No fee is debited, i.e. SPMs are ignored, and the coins are/should be returned on hang up!

The extract of the state table answers that. A 26 event while in D3, i.e. test mode, causes a transition to state 03 which is the base state to start a normal call. So, yes, it forces normal call mode when the light sensor is exposed to light. So yes, its a normal call but with the door open, nothing more and nothing less. :-) Presumably it encourages the engineer/technician to call back to base once they've done whatever they've been sent to do.

Extract from State Table

21 4F2D 5349

22 4F2F 534A

23 4F31 534B

24 4F33 534C

25 4F35 534D

26 4F37 534E D3 03 00 0A 5C77 75 59 01 12 20 21 88 42 31 84

The entry state is on the left, the next state is on the right and the event that causes the transition is in the middle:

D3 in Version 15 software

D3" " 11" " D4"

" 12" " D4"

" 13" " D4"

" 14" " DC"

" 15" " D5"

" 16" " D5"

" 20" " D5"

" 26" " 03"

" 29" " 15"

" 30" " D7"

" 31" " D7"

" 34" " D6"

" 35" " D6"

" 36" " D6"

" 37" " D6"

" 38" " D7"

" 40" " 15"

" 41" " 15"

" 43" " D9"

" 4E" " D1"

" 54" " D8"

" 55" " D8"

" 6E" " E0"

" 72" " D9"

" 7A" " DA"

" 7B" " D5"

" 7C" " FC"

" 7F" " E8"

D3 in Version 4 software