Toshiba DP120F Service Manual page 309

4. NCU PBA ..................................................................................................... 7-77
4.1 Line Path Switching Control Circuit ................................................................ 7-79
4.2 Dial Pulse Generation Circuit ......................................................................... 7-81
4.3 Line Current Detect Circuit ............................................................................. 7-83
4.4 CI Detect Circuit ............................................................................................. 7-85
4.5 Line Monitor Circuit ........................................................................................ 7-87
4.6 Hook Detect Circuit (US/CA models only) ...................................................... 7-90
5. MOTHER PBA ............................................................................................. 7-91
6. OPERATION PANEL PBA ........................................................................... 7-93
7. LVPS ............................................................................................................ 7-95
7.1 Power Supply Voltage Generation ................................................................. 7-96
7.2 Stabilizing Circuit ............................................................................................ 7-97
7.3 Power Output Control Circuit .......................................................................... 7-98
7.4 Heater Drive Circuit ........................................................................................ 7-99
8. HVPS ............................................................................................................ 7-100
9. PC I/F PBA ................................................................................................... 7-102
10. MODEM PBA ............................................................................................... 7-103
11. TEL PBA ...................................................................................................... 7-104
12. MEMORY PBA ............................................................................................. 7-105
13. Bypass Tray Control Circuit ...................................................................... 7-106
14. OPTIONAL TRAY PBA ................................................................................ 7-108