Note
Review: CQ, Aug 1960, p. 71.
The Electrocom FSC-250 is a Frequency Shift Converter designed to provide stable radio-teletypewriter (RTTY) performance. It is typically used in conjunction with the TK-100 Tone Keyer to create a complete RTTY system.
It receives audio tones from a single sideband (SSB) receiver and converts them back into DC pulses suitable for operating a teleprinter. It features an accurate scope tuning indicator to allow for the proper frequency setting of equipment.
Components and Connectivity
– Plug-in Filters: Like the TK-100, the FSC-250 uses plug-in bandpass filters (e.g., BPF 2125A for Mark and BPF 1275A or 2975A for Space) to adapt to different tone frequencies.
– DC Loop: It includes a DC loop to operate the teleprinter.
– Motor Control: It can be wired to automatically start the teleprinter motor upon receiving a "mark" tone and turn it off after one second of a continuous "space" tone.
– Optional Filtering: It contains an internal plug for an optional bandpass input filter to eliminate adjacent channel interference.
Operational Features
– Transceive Capability: If the same tone frequencies are used in both the tone oscillator (TK-100) and the converter (FSC-250), the system can be used for transceive operations.
– Monitoring: The converter's scope can be used to monitor the output of the tone oscillator during transmission to ensure the keyer is operating correctly.
– Local Test: The unit supports a "Test" mode that allows the user to monitor mark and space tones on the FSC-250 indicator and type on the teleprinter without going on the air
