I found 3 different voltage levels in use: 0V (battery minus,
this is connected to the core module), 3V (battery plus, this
is connected to the case) and 1.5V (half battery voltage).
The 1.5V is generated by the core module and seems to be the
low level for the display logic. For easy description, I call
these levels -, + and LGND.
There is no Pin1 mark, so I numbered the contacts this way:
1 Button 'Mode' (against +)
2 Button 'Transmit' (against +)
3 Reset contact point (against +)
4 Display clock output (32kHz square wave, H=+, L=LGND)
5 Display address strobe (L-active, H=+, L=LGND)
6 Display data strobe (L-active, H=+, L=LGND)
7 Beeper output (4096Hz square wave pulse packets, against +)
8 Battery - (battery minus is directly connected to this pin only)
9 - (this is the 'official' minus, 1.5uF against + on mainboard)
10 transceiver coil/antenna (against +)
11 LGND output (100nF against + on mainboard)
12 C+ (a 100nF capacitor is connected between 12 and 13...)
13 C- (probably for generating LGND)
14 Battery +
15 Display Bit 1 output (H=+, L=LGND)
16 Display Bit 2 output (H=+, L=LGND)
17 Display Bit 6 output (H=+, L=LGND)
18 Display Bit 7 output (H=+, L=LGND)
19 Display Bit 5 output (H=+, L=LGND)
20 Display Bit 4 output (H=+, L=LGND)
21 Display Bit 3 output (H=+, L=LGND)
22 Display Bit 0 output (H=+, L=LGND)
23 Button 'Select' (against +)
24 Button 'Set' (against +)