NIPPON OKI ODS 5550 1 MARINE TELEPHONE MFG NO 179 #3

NIPPON OKI ODS 5550 1 MARINE TELEPHONE MFG NO 179

The Nippon Oki ODS 5550-1 is a rugged, medium-frequency (MF) marine radiotelephone designed for reliable voice communication on board commercial and recreational vessels. As indicated by the manufacturing number (179) and the “#3” identifier, it was part of a specific production batch. The “SEO” in the product description likely stands for the manufacturer, supplier, or a specific model variant, possibly San Equipment Office or a similar entity.

This unit was a crucial piece of equipment before the widespread adoption of VHF radios and satellite communications, allowing ships to communicate with each other and with coastal telephone stations, connecting to the public switched telephone network (PSTN).

Key Features & Specifications:

• Type: Marine Radiotelephone

• Frequency Band: Medium Frequency (MF). Typically operated in the 1.6 – 4.0 MHz range, allowing for “skip” propagation and longer-range communication than VHF, especially at night.

• Channels: Likely featured a selection of crystal-controlled ITU (International Telecommunication Union) channels for ship-to-ship and ship-to-shore communications.

• Power Output: Estimated to be in the range of 50 to 150 watts PEP (Peak Envelope Power), providing a good balance between communication range and power consumption.

• Control Unit: The ODS 5550-1 is the main control unit/transceiver. It would have been installed in the vessel’s wheelhouse or radio room.

• Operation: Simplex operation (transmit and receive on the same frequency, taking turns).

• Construction: Built with a heavy-duty metal chassis and front panel, designed to withstand the harsh marine environment, including moisture, salt spray, and vibration.

• Interface: Features a traditional, straightforward interface with a channel selector, squelch control, volume control, and a large, clear meter for measuring signal strength and power output.

Typical System Components:

A fully functional system would have consisted of several components:

1. ODS 5550-1 Control Unit/Transceiver: The main unit you have.

2. DSS 5550-1 Desk Top Microphone/Speaker: A combined handset or a separate microphone and loudspeaker unit.

3. Power Supply Unit: A separate unit to provide the required DC power (typically 12/24V DC) from the ship’s batteries.

4. Antenna Coupler/Tuner: A critical matching unit to tune the vessel’s long-wire antenna to the specific frequency in use for efficient transmission.

Historical Context and Usage:

• Era: This telephone is a product of the 1970s or early 1980s, representing the technology standard before fully synthesized and digital radios became common.

• Primary Use: It was used for:

  • Ship-to-Shore Calls: Connecting to a coastal radio station (like “Koko Head” in Hawaii or “Point Reyes” in California) to be patched into the international landline telephone system.

  • Ship-to-Ship Communication: For conversing with other vessels within range.

  • Listening to Marine Weather Bulletins: Broadcast by coast guards and meteorological services on specific MF frequencies.

• Modern Status: This equipment is now considered obsolete for primary maritime communication. It has been superseded by:

  • VHF Radios: For short-range communication.

  • SSB (Single Sideband) Radios: A more efficient evolution of MF/HF radio.

  • Satellite Phones (e.g., Inmarsat, Iridium): For global, reliable communication.

  • GMDSS (Global Maritime Distress and Safety System) Equipment.