TCI-20, 20 Circuit Telegraph Decode

Product Information

TCI-20 with PCB Boards

TCI-20 with PCB Boards

The Telegraph Coded Input (TCI) may be added with any other option into the System 3505 Prism LX™. The TCI allows the System 3505 Prism LX™ to receive an alarm via a coded telegraph alarm line.

The alarm can either be an open or closed index type. Boxes of the “open” or “closed” index can be mixed on the same alarm circuit. The TCI-20 supports any of the following PCBs: 100 mA, 24 VDC, NO or NC dry contact. The alarms into the System 3505 Prism LX™ can be mixed in any order that may be needed to make a complete system. That is, Ckt. 1 can be 24 VDC, Ckt. 2 can be NC dry contacts, Ckt. 3 100 mA and so on.

All TCI options convert coded alarm signals into the proper format for processing by the System 3505 Prism LX™, as well as providing screw terminals to which the coded alarm inputs may be connected. The standard ribbon cable is four feet. An optional ribbon cable of up to 25 feet is available.

The TCI option, when connected to the telegraph circuit, will input code to the System 3505 Prism LX™ for processing. The code will be processed and printed out on a round-by-round basis. The screen on the System 3505 Prism LX™ will display the incoming circuit number, as well as show the box decoding. It will also display that the alarm is an incoming telegraphic alarm. The audible alert will be activated.

Optional PCBs configure the inputs to 100 mA, 24 VDC, or NO or NC dry contacts. PCBs are installed on the TCI-20 motherboard. One PCB is required per each circuit to be monitored. Mix & match up to 20 PCBs per TCI-20. Note: once installed, the TCI-20 precludes the TCI-1 or TCI-6.


  • 20 circuit telegraph Interface
  • Requires one 24 VDC, 100 mA or NO/NC dry contact PCB module per circuit (sold separately)
  • Mix & match up to 20 input cards
  • Supports open index and closed index box formats
  • Powered by System 3505 Prism LX™.
  • Expansion beyond 20 circuits possible with additional TCI-20 cards and software
  • NFPA-72 Compliant


Input Alarm Signal (selectable by alarm interface board):

Loop current: 35 – 200 mA for closed loop Repeater Buss: +24 VDC

NO Dry relay contact

NC Dry relay contact

Open or closed index decoding (auto detected by SYSYTEM 3505 Prism LX™) with any of the above

Incoming Box Speed:

Open Index (Municipal box type): Any starting box speed between 1/8-4 seconds. With a +- 50% speed change per round. No adjustments needed. “Fail Safe” Takeover Point: When 1:2:5:6.25 code wheel ratio is exceeded by +50%, the SYSTEM 3505 Prism LX™ will restart box number decoding to attempt to salvage the box number being decoded.

Closed Index (Security type box): 1/8-1.6 seconds if 2 teeth removed

Module Power: Supplied by System 3505 Prism LX™

Decodes: 1-6 digit boxes (except box numbers 1, 11, 111, 1111, 11111, and 111111)

Box Storage: 30 alarms, 5 rounds each. To avoid losing rounds, additional rounds will roll over as if they were a new box (first box circuit, no limit on rounds)

Make Break Ratio: Standard is 50/50 per digit, however, may deviate to 1::99 or 99:1, but modifies +- 50% speed change per round for Open Index and +-25% for Closed Index.