Schematic __full__: Icom Ct-17
The signal enters via the DB9 connector. The CT-17 uses only three pins of the RS-232 standard: , Pin 3 (TxD) , and Pin 5 (Ground) .
This is where the schematic gets interesting. The phototransistor side of the optocoupler is powered entirely by the (taken from the Ring of the 3.5mm jack). This is the heart of the isolation. icom ct-17 schematic
The official Icom schematic is not a complex, multi-layer PCB monstrosity. It is a beautifully straightforward example of mid-1990s analog/digital design. Let’s break it down into functional blocks. The signal enters via the DB9 connector
If you are looking at a hand-drawn or scanned original schematic, here is the bill of materials you should expect: The phototransistor side of the optocoupler is powered
Before examining the schematic, it's crucial to understand what the CT-17 does. It is a bi-directional level converter and signal isolator. Your computer speaks RS-232 (using ±12V logic). Your Icom radio speaks CI-V (using TTL levels – 0V and 5V, inverted logic). Connecting them directly would release magic smoke. The CT-17 bridges this gap safely using optocouplers to prevent ground loops and RF feedback.
The CT-17 is essentially a bidirectional level converter between RS-232 (±12V) and TTL (0–5V) for Icom’s CI-V bus. Key parts include:
