Pins
Sa-Sg and SDp : display segments and decimal point
D0 to D10: display grid signal for each digit, and keyboard multiplexing
K0 to K3 and K0' and K3': keyboard and switch multiplex lines
TP, TM, S', TR and MT are printer controls
VC: onboard clock
ACL looks like a clear on power up automatic clear

Voltages are given for this example
Vg  24.3 to 29.7V
VGG -11.7 to 14.3V
Vss 0V