Figure 4-6: Internal View of Hydran 201Ci-1 
 
4.  Digital Display Circuit Board Cover:  This cover protects the display circuit board, 
which includes the digital voltmeter and the connections of the two push-buttons. 
 
5.  Electronic Circuit Board:  The circuit board incorporates all the electronic functions 
of  the  H201Ci-1:  H201Ti  TDM  pulse  decoder,  alarm  relay  drivers,  configurable 
analog  output  amplifiers,  display  signal  conditioning,  supervisory  link  supply, 
communication  ports  and  modem  (optional)  management,  enclosure  heater 
control, and ac supply voltage selector.  See  Appendix C.3 for a simplified block 
diagram of the circuit. 
 
6.  Main  Terminal  Block:    The  ac  power  supply,  the  analog  output,  the  three alarm 
relays  (Alarm  1  =  Gas  High,  Alarm  2  =  Gas  High-High,  and  System  OK),  the 
supervisory  link  cables  and  the  RS-485  LAN  are  connected  to  this  40-screw 
terminal block.  For wiring details, see Table D - 11 in Appendix D.