equipped with a heartbeat LED

The  408M is equipped with a heartbeat LED that  indicates processing  activity  on  the PCB.  (The 408M peripheral processor  is  operating when  the heartbeat LED  is flashing.)  The KSU1 operation LED (located  next  to the power switch) is  tied to the  408M heartbeat LED.   Therefore,  when  the  LED next to the power switch is flashing,  the 408M is active. The  KSU1-408M  has three ribbon cables: •   located at the upper  right and oriented  in a horizontal  position, the J1  cable is used to interface a COM4  if required to expand  the system CO line  capacity. •   located at  the  upper center  and oriented  in  a  vertical position,  the J4  cable  is  used to interface the DX-80 CPM. •   located at the upper  center  and oriented  in a vertical position,  the J5 cable  connects to  the standard APM4 installed  in KSU1. Each CO line circuit  incorporates  over-voltage  protection, ring  detector, loop  detector, loop/pulse-dial relay,  current sink circuit, coupling/isolation transformer (impedance  600:600), hybrid  circuit, CODEC & filter,  polarity guard  circuit  and Radio  Frequency noise filter. The  fourth CO line port is equipped with  CNG Fax  Tone  Detection circuitry.   When  programmed  as  a “FAX” line, this circuit will automatically engage the FAX Tone detector.  If FAX tone is detected, the system routes  the call  to the analog port  designated as the destination for  fax calls.