In the below picture on the left is the PCR-SIN03V12F20-C, this is the unit that steps up the 12vdc to 70v 20Hz to make the bell ring.
The picture on the right is the dc to dc step down conerter, search LM317 DC-DC, its very important to power this unit with the 12v power supply
you intend to use and ajust the output to 5v before using it in this project.

       


click picture to enlarge

Below are the Sketches for Phone Ringer that works, it may not be the best put you can change it to suit your own designs

/*
  MerrittSoft
  Phone_Ringer
  30/03/2020
  Language: C++/Arduino
  Thank you to those people that made the Libarays in this project posable.
*/

#include <ESP8266WiFi.h>
#include <ESP8266WebServer.h>


ESP8266WebServer server;


const int output = D1;
const int output2 = D2;
const int button5 = D5;
const int button6 = D6;
const int button7 = D7;
const int button8 = D8;

char* ssid = "Network Name";
char* password = "Network Password";

int Ringing1 = 0;
int Ringing2 = 0;
int Ringing3 = 0;
int Ringing4 = 0;


void setup()
{
  pinMode(output, OUTPUT);
  pinMode(output2, OUTPUT);
  digitalWrite(output, LOW);
  digitalWrite(output2, LOW);

  pinMode(button5, INPUT);
  pinMode(button6, INPUT);
  pinMode(button7, INPUT);
  pinMode(button8, INPUT);


  WiFi.begin(ssid, password);
  WiFi.hostname("Phone_Ringer");
  WiFi.mode(WIFI_STA); // added works with some boards to stop the wifi broadcast.
  //WiFi.mode(WIFI_AP_STA); // added works with some boards to start the wifi broadcast.
  Serial.begin(115200);
  while (WiFi.status() != WL_CONNECTED)
  {
    Serial.print(".");
    delay(500);
  }
  Serial.println("");
  Serial.print("IP Address: ");
  Serial.println(WiFi.localIP());

  server.on("/", []() {
    server.send(200, "text/plain", "Meltronica");
  });

  // below are the commands that activate the Ring Pattons
  // eg. the /RING1 is the command you add to the end of the ip address of the Phone_Ringer (NodeMCU) eg. 10.220.1.20/RING1   This can be done in a Web Browser on the same network

  server.on("/RING1", RING1);

  server.on("/RING2", RING2);

  server.on("/RING3", RING3);

  server.on("/RING4", RING4);


  server.begin();
}

void loop() {

  if (WiFi.status() != WL_CONNECTED)
  {
    ESP.reset();
  }

  server.handleClient();

  Ringing1 = digitalRead(button5);
  if (Ringing1 == HIGH) {
    delay(1000);
    Ringing1 = digitalRead(button5);
    if (Ringing1 == HIGH) {
      RINGSOUND1();
    }
  }
  Ringing2 = digitalRead(button6);
  if (Ringing2 == HIGH) {
    delay(1000);
    Ringing2 = digitalRead(button6);
    if (Ringing2 == HIGH) {
      RINGSOUND2();
    }
  }
  Ringing3 = digitalRead(button7);
  if (Ringing3 == HIGH) {
    delay(1000);
    Ringing3 = digitalRead(button7);
    if (Ringing3 == HIGH) {
      RINGSOUND3();
    }
  }
  Ringing4 = digitalRead(button8);
  if (Ringing4 == HIGH) {
    delay(1000);
    Ringing4 = digitalRead(button8);
    if (Ringing4 == HIGH) {
      RINGSOUND4();
    }
  }

}

void RING1()
{
  delay(1000);
  server.send(204, "");
  RINGSOUND1();
  return;
}

void RING2()
{
  delay(1000);
  server.send(204, "");
  RINGSOUND2();
  return;
}

void RING3()
{
  delay(1000);
  server.send(204, "");
  RINGSOUND3();
  return;
}

void RING4()
{
  delay(1000);
  server.send(204, "");
  RINGSOUND4();
  return;
}
/*            Below you can make the ring pattons you want for the 1 to 4 buttons by adding
              digitalWrite(output, HIGH);
              digitalWrite(output2, HIGH);
              delay(100); changing the delay time
              digitalWrite(output, LOW);
              digitalWrite(output2, LOW);
              delay(100); changing the delay time
*/
void RINGSOUND1()
{
  digitalWrite(output, HIGH);
  digitalWrite(output2, HIGH);
  delay(441);
  digitalWrite(output, LOW);
  digitalWrite(output2, LOW);
  delay(163);
  digitalWrite(output, HIGH);
  digitalWrite(output2, HIGH);
  delay(441);
  digitalWrite(output, LOW);
  digitalWrite(output2, LOW);
  delay(1974);
  digitalWrite(output, HIGH);
  digitalWrite(output2, HIGH);
  delay(441);
  digitalWrite(output, LOW);
  digitalWrite(output2, LOW);
  delay(163);
  digitalWrite(output, HIGH);
  digitalWrite(output2, HIGH);
  delay(441);
  digitalWrite(output, LOW);
  digitalWrite(output2, LOW);
  return;
}


void RINGSOUND2()
{
  digitalWrite(output, HIGH);
  digitalWrite(output2, HIGH);
  delay(2000);
  digitalWrite(output, LOW);
  digitalWrite(output2, LOW);
  delay(1000);
  digitalWrite(output, HIGH);
  digitalWrite(output2, HIGH);
  delay(2000);
  digitalWrite(output, LOW);
  digitalWrite(output2, LOW);

  return;
}


void RINGSOUND3()
{
  digitalWrite(output, HIGH);
  digitalWrite(output2, HIGH);
  delay(3000);
  digitalWrite(output, LOW);
  digitalWrite(output2, LOW);
  delay(1000);
  digitalWrite(output, HIGH);
  digitalWrite(output2, HIGH);
  delay(3000);
  digitalWrite(output, LOW);
  digitalWrite(output2, LOW);

  return;
}


void RINGSOUND4()
{
  digitalWrite(output, HIGH);
  digitalWrite(output2, HIGH);
  delay(3000);
  digitalWrite(output, LOW);
  digitalWrite(output2, LOW);
  delay(2000);
  digitalWrite(output, HIGH);
  digitalWrite(output2, HIGH);
  delay(3000);
  digitalWrite(output, LOW);
  digitalWrite(output2, LOW);

  return;
}