IS220PDOAH1A - Discrete Output Pack

IS220PDOAH1A - Discrete Output Pack IS220PDOAH1A - Discrete Output Pack

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Part Number: IS220PDOAH1A
Manufacturer: General Electric
Country of Manufacture: United States (USA)
Number of relay channels: 12
Size: 8.26 cm high x 4.19 cm wide x 12.1 cm deep
Technology: Surface-mount
Series: Mark VIe
Function: Discrete Output pack

Functional Description

IS220PDOAH1A is a discrete output pack developed by GE. It is part of the GE Speedtronic Mark VIe gas turbine control system. It connects one or two I/O Ethernet networks to a discrete output terminal board via an electrical interface. The pack includes a processor board shared by all Mark VIe distributed I/O packs as well as an acquisition board dedicated to the discrete output function.


  • The number of relay channels in a single PDOA pack is 12 relays (different types depending on the terminal board)
  • 15-pack inputs are monitored by a relay and a coil. The type of terminal board used, as determined by the ID chip, influences the selection of monitor feedbacks.
  • The I/O pack response time is approximately 6 ms from Ethernet command to output.
  • The pack can control up to 12 relays and accepts feedback from the terminal board. There are magnetic relays (TRLYH1B, C, D, and F terminal boards) and solid-state relays (TRLYH1E boards) available. The pack is powered by three-pin power input and two RJ45 Ethernet connectors. Output is via a DC-37 pin connector that is directly connected to the associated terminal board connector. Indicator LEDs provide visual diagnostics, and an infrared port allows for local diagnostic serial communications.


It works with six different types of discrete (relay) output terminal boards, including TRLY and SRLY boards, but not DIN-rail mounted DRLY boards. The number of I/O packs used in a signal path is referred to as the control mode:

  • Simplex employs a single I/O pack and one or two network connections.
  • Dual employs two I/O packs with one or two network interfaces.
  • TMR employs three I/O packs, each with one network connection.


Installing the PDOA pack:

  • Securely mount the terminal board of choice.
  • Insert one simplex PDOA I/O pack or three TMR PDOA I/O packs directly into the terminal board connectors.
  • Use the threaded studs next to the Ethernet ports to mechanically secure the packs. The studs fit into a terminal board-specific mounting bracket. The bracket should be positioned so that no right-angle force is applied to the DC37 connector between the pack and the terminal board. The adjustment should only be needed once during the product's lifetime.
  • Depending on the system configuration, connect one or two Ethernet cables. The pack will work with either port. When using dual connections, it is common practice to connect ENET1 to the network associated with the R controller.
  • Connect the pack to power by plugging in the connector on the pack's side. This connector does not need to be inserted with the power disconnected from the cable because the I/O pack has an inherent soft-start capability that controls current inrush on power application.
  • Configure the I/O pack as required.



  • The processor board is linked to an acquisition board that is dedicated to the I/O pack function. When input power is applied, the soft-start circuit increases the voltage available on the processor board. The local power supplies are turned on in sequence, and the processor reset is disabled. After completing self-test routines, the processor loads application code specific to the I/O pack type from flash memory.
  • The application code reads board ID information to ensure that the application code, acquisition board, and terminal board are all correctly matched. With a good match, the processor attempts to establish Ethernet communications, beginning with a network address request.
  • The address request employs the industry-standard dynamic host configuration protocol (DHCP) and the terminal board's unique identification. Following Ethernet initialization, the processor programs the onboard logic executes the application, and allows the acquisition board to start up.

Relay Command Signals

  • The relay command signals are used as the first stage of signal conditioning and level shifting to connect terminal board outputs to control logic. Each output is an open collector transistor circuit with a current monitor that detects when the output is selected and connected to a load.
  • When an output is picked up and connected to the terminal board, the status LEDs and monitor outputs illuminate. If the output is selected but no load is detected, the status LED will turn off and the monitor line will be false.

Output Enable

  • During power application, all outputs are disabled until a series of internal self-tests are completed. An enable line reflects the status of all required operating conditions. This function provides an independent path to ensure that relays remain dropped out during power-up and initialization.

Status LEDs

  • PWR LED (Green)
    • Indicates the presence of control power.
    • Provides a quick visual confirmation of power supply to the pack, ensuring operational readiness.
  • ATTN LED (Red)
    • Indicates pack status and various conditions:
    • LED out: No detectable problems with the pack.
    • Solid on: Indicates a critical fault preventing pack operation, such as hardware failures or absence of application code.
    • Flashing quickly (1⁄4 cycle): Indicates an alarm condition, such as incorrect pack placement or application code loading errors.
    • Flashing at medium speed (3⁄4 cycle): Indicates the pack is not online.
    • Flashing slowly (2 cycles): Indicates a request to draw attention to the pack, commonly used during factory tests or to confirm physical location.
  • LINK LED (Green)
    • Provided for each Ethernet port.
    • Indicates the presence of a valid Ethernet connection.
    • Ensures that network connectivity is established and maintained, facilitating communication with external devices or systems.
  • TxRx LED (Yellow)
    • Provided for each Ethernet port.
    • Indicates transmission or reception of data over the respective port.
    • Offers real-time feedback on data transfer activity, aiding in troubleshooting and monitoring network traffic.

WOC has the largest stock of Speedtronic Mark VIe Spares and we can repair your faulty spares with a warranty. WORLD OF CONTROLS can also supply unused and rebuilt components backed up with a warranty. Our team of experts is available round the clock to support your urgent needs related to critical spares, contact us.



What is IS220PDOAH1A?
It is a discrete output pack and is part of the GE Speedtronic Mark VIe gas turbine control system.

What is the purpose of the green LINK LED?
The green LINK LED, provided for each Ethernet port, indicates the presence of a valid Ethernet connection, ensuring network connectivity.

What does the yellow TxRx LED indicate?
The yellow TxRx LED, also provided for each Ethernet port, indicates when the pack is transmitting or receiving data over the respective port, offering real-time feedback on data transfer activity.

How do these LEDs contribute to system monitoring?
These LEDs offer quick visual feedback on pack power, status, network connectivity, and data transmission activities, aiding in system monitoring, troubleshooting, and maintenance efforts. They help operators quickly identify potential issues and ensure the smooth operation of the control system.