Monitor Your Fire Panel (FACP) via Printer Port (ASCII) - Autocall Example

By Andrew Erickson

January 15, 2023

For fire panels, especially older ones, one of the most common ways for alarm data to be emitted is via a traditional printer port. While this used to literally result in a printed paper record, it's now much more popular to display the ASCII text (raw or processed) on your fire alarm display screen.

Autocall TFX fire panel diagram

This diagram from the manufacturer's user manual shows the Autocall fire panel connected to a printer or UL-listed terminal. This is an interface we can leverage to connect a modern Muxpad mediation device.

Let's discuss the basics this type of alarm monitoring, then review specific fire panels from:

  • Autocall
  • Edwards (EST)
  • FCI
  • Gamewell
  • Hochiki
  • Mircom
  • Notifier
  • Simplex

What alarm data can I see from the FACP printer port's output?

Using a printer port, you can have access to important information such as the FACP's status, alarms detected, and sensor readings. These obviously vary based on the specific capabilities and capacity of your FACP.

You need a mediation device that can collect data from the printer port and transmit it to your central monitoring location via newer transport, usually LAN, radio, or wireless network.

Advantages of monitoring alarms via printer port

In theory, the printer port is one of the easiest ways to monitor your Fire Alarm Control Panel (FACP). By connecting your printer port to the right hardware, you can easily monitor fire alarms as they occur. This makes it easier for emergency personnel to respond quickly and effectively in the event of a fire or other emergency.

The Printer Port connection is a simple setup that requires minimal wiring or equipment. It uses the same type of port as most (historical) standard printers and computers, making it easy to connect.

This information is displayed in an easy-to-read ASCII format (human-readable) that can be quickly understood and interpreted by emergency personnel.

Using a printer port to monitor your FACP is an easy and efficient way to ensure that emergency personnel have all the information they need in order to respond quickly. It gives you access to important information that can help save lives, and its (sometimes) simple setup makes it convenient for those who don’t want to invest in expensive hardware or installations.

Problems with using ASCII text from the printer port

Unfortunately, compatibility can be a major problem because there is no declared standard for ASCII (text-based) communication. Your intermediary device must know how to extract information if you don't simply want to see the raw text summary of the alarm.

Imagine you want to extract timestamp, alarm description, or other data so you can trigger different alerts for emergencies vs. maintenance/status events. Some device in your overall installation must be able to parse (interpret) the long ASCII messages to intelligently sort and filter them.

How to monitor your Autocall TFX-500M or TFX-800M (by Grinnell)

The manual for these fire panels (I found one from 1997) calls out the "PIM-550 Printer Interface Module Assembly No. 976018". This is the hardware option you'll need (pre-installed on many units sold) to be able to collect text output. It "provides galvanic isolation between the Autocall TFX-500/500M/800/800M fire control panel and a serial-interface UL-listed printer (P/N 920020).

This port was originally designed for use with "LX -300 9-Pin Dot Matrix Printer PIN 976264" or "Two Printer Options-Autocall Printer option (PIN 976018 or 976264)-provides a permanent printed record of system activity" (up to 31 of them, according to the manual!).

The printer is connected to the "Serial Interface Module", which "provides an isolated interface between AUTOCALL TFX, AL-1500 and AL-1500E control panel RS232 or 20 mA circuits and peripheral devices such as printers and video terminals."

Features (of the Serial Interface Module):
  • Provides electrical ground isolation between control equipment and UL listed printer, video terminal, or any other UL listed peripheral devices. Isolation allows for proper ground fault monitoring of the RS-232 cable.
  • Converts 20 mA signals to RS232 levels to drive UL listed terminal devices.
  • Eliminates the need for a separate printer interface module, required by the TFX for isolation.

Fortunately, we can connect a different device to this serial port in the modern era.

As you can see in the diagram here, there actually was originally provision for using either a physical paper printer OR "any UL-1950-listed terminal". Remember that other labs like ETL are equally valid for the purposes of building a government-approved fire protection system.

What you will do is connect the serial port of your Autocall TFX-500 (or TFX-500M, or TFX-800, or TFX-800M) to a device like the Muxpad. The Muxpad will forward all received alarms to your central Prism LX master station for display.

In this way, you'll collect all of your fire alarms in one place (even across an entire city, if you spread that far). With the right remote annunciators in place, everyone on your team who needs to see an urgent fire alarm will be able to.

Use a Muxpad to conveniently monitor your fire panels (FACP)

The Muxpad is a versatile device that allows fire system installers to monitor their FACP via printer port (ASCII). This eliminates the need to connect multiple fire panels to a network of independent printers, saving time and money on installation costs.

Furthermore, this approach provides greater fire alarm visibility in larger fire protection systems. Imagine having a single alarm list on a central computer console vs. having dozens of individual printers to watch. In the end, fire safety is improved and fire risk reduced while saving budget dollars.

Call Digitize for engineering help with monitoring your FACP via serial/printer port

As you can see from all of the technical data I've assembled in this guide, this stuff can be pretty complex. Fortunately for you, we engineered our Muxpad device specifically for compatibility with every device listed in this article.

As always, it's best to actually speak with an expert before continuing with your project planning. To get started, all you need to do is call us here and ask to speak with one of our fire protection system engineers.

Call Digitize at 1-800-523-7232 or email us at

Andrew Erickson

Andrew Erickson

Andrew Erickson is an Application Engineer at DPS Telecom, a manufacturer of semi-custom remote alarm monitoring systems based in Fresno, California. Andrew brings more than 17 years of experience building site monitoring solutions, developing intuitive user interfaces and documentation, and...Read More