IBM PC 300 Maintenance Service Manual page 124

JP3: TEL –The connector for Modem with internal voice connector.
Pin No. Function
1 Phone-in
2,3 GND
4 Mono-out
JP1: STR Enable
Pin No. Function
Close STR Enable
Open STR Disable (Default)
JP14: Case Open
Pin No. Function
1 Signal
2 GND
JP13: Safe Mode/Recovery/Normal
Pin No. Function
1-2 close Normal (Default)
2-3 close Safe Mode
1-2-3open Recovery
JP16: Top Block Lock
Pin No. Function
Open Top Block Lock
Close Top Block Unlock (Default)
JP15: Timeout Reboot
Pin No. Function
Open Timeout Reboot.
Close No Reboot on Timeout. (Default)
JP17: Onboard Sound function (Optional)
Pin No. Function
1-2 close Enabled Sound.(Default)
2-3 close Disabled Sound.
J13/ J20: USB Port Selection (Optional)
Pin No. Function
1-2 close Front Panel USB Port Enabled.
2-3 close Back Front Panel USB Port Enabled.
124