Phone that takes input from a rotary dial(check Wikipedia: Rotary dial).
The dial produces pulses where [1, 9] pulses correspond to the numbers [1, 9], and 0 is represented by 10 pulses. Similar to the dial demonstrated here and pictured above.
The expected circuit is:
Rotary Dial Arduino
/---------------------- readyPin (pin 7)
/- ready switch (NO) -- pull-up resistor -- VCC
/-- pulse switch (NC) -- pull-up resistor -/
\ \---------------------- pulsePin (pin 8)
\------------------------------------------ GND
HT1621 DISPLAY
pin 1 ------------------------------ VCC
pin 2 --470 ohm resistor ----------/
pin 3 ------------------------------ GND
pin 4 ------------------------------ DATA (pin 11)
pin 5 ------------------------------ WD (pin 10)
pin 6 ------------------------------ ~CS (pin 12)
INPUT BOARD
/-------------------- callPin (pin 9)
/- Call Button -- pull-up resistor ------- VCC
/-- Back Button -- pull-up resistor ------/
\ \--------------------- backPin (pin 6)
\- Clear Button -- pull-up resistor ------- VCC
\ \--------------------- clearPin (pin 5)
\---------------------------------------- GND
SIM 800L
VCC ------------------------------ 4.2V BAT INPUT
GND ------------------------------ GND
RXD ------------------------------ Software Tx (pin 2)
TXD ------------------------------ Software Rx (pin 3)
RING ------------------------------ Call_Detect (A3)
SIM 800L TO RECEIVER
MIC +,- -------------------------- ELECTRET MIC
SPK +,- -------------------------- 8 ohm SPEAKER
I soldered everything to a prototyping board and powered the board with two 18650 cells in parallel.
👍 The circuit looks great and ready to take on some calls 
