/* Imported from Wayback Machine

 Original URL : https://www.retrobrewcomputers.org/doku.php?id=builderpages:speed3ple:ecb-cassetteif
 Snapshot date: 2025-12-12
 Generator    : wayback-archiver

*/

ECB-Cassette IF

Text	Images
Home made alu bracket for the 3.5mm jacks. I made both for 300 baud and checked if they could “talk” correctly to each other. (as in backup/restore). Turns out I had to measure&select the timing capacitor C2 very precise to get 100% reliable interchangeable operation. I have now “upgraded one of the board to 600baud. I will modify the bracket to include the send/receive activity LEDs. Info: This pcb has ground plane on both side so no problem with the screws.
Cassette IF in action in a backplane-4:
Cassette IF signal out on Scope: This is the “Kansas City” standard, one of several cassette formats in use at the time (mid 70's). Kasas City format use an continuous audio stream of a tone and shift that tone between 2400hz and 1200hz to indicate 1 or 0. 8 cycles of 2400hz represent a “1” bit or a MARK and 4 cycles of 1200hz represent a “0” bit or a SPACE.
Cassette Interface in use: To send a file to tape: PIP PUN:=<filename.hex>[E]
Cassette IF and technical document:
Interconnecting 2 SBC and sending/receiving data through audio cable at 300baud: