Check the listing for details. TACH TACHOMETER SIGNAL BOOSTER, 3~16V In -> 48~63V Out, compare to MSD 8920. Condition: New. Listed at 29.39 USD. DOCUMENT DOWNLOADS AVAILABLE FOR THIS PRODUCTFAQ: https://drive.google.com/file/d/1tKwe6ALWturbYO-EL0yvutQrk6f0vvzJ/view?usp=sharing INSTRUCTIONS: https://drive.google.com/file/d/1dWe6wmC9p4anStHIVQ3S_dO8g3eOKeTF/view?usp=sharing USING PULLUP RESISTORS: https://drive.google.com/file/d/1QLjjXIbRG744A18xEpcQTxeahPeJVPEH/view?usp=sharing TYPICAL HOOKUP: https://drive.google.com/file/d/1m8VWK3j2LOeQqiD8E4KJzi_WeOd8xaAQ/view?usp=sharingWM CATALOG: https://drive.google.com/file/d/1sY_qYCQMJ6KPikZYNQ9rVLyK7spUNtxH/view?usp=sharing BOOST ECU TACH SIGNALS TO FEED 24V AND BACK-EMF STYLE TACHOMETERS IMPORTANT:The BTAC2 can NOT substitute for the MSD 8920 in applications with current-mode tachometers, such as pre-'74 Mustangs and Pantera Veglias, vintage Sun tachs with external signal boxes, vintage OEM rally packs, etc. The BTAC2 works ONLY for voltage-mode tachos that require high voltage to trigger. Please contact us if you are unsure about your application. Modern aftermarket tachs all work fine with a 12V digital signal, but what if the old tach in your dashboard can't see the square wave from your brand new ignition? Before 1995, many tachs expected to see a high-voltage "spike" from a discharged ignition coil, so they flatline when connected to a digital tach output like an ECU or MSD 6AL. This little device can solve your problem, using a miniature coil to mimic the action of an ordinary ignition coil. It produces a minimum 48V+ from a 12V supply and will trigger with as little as 0.8V. It's compatible with all tach correctors and adaptors providing a digital output, including our own BTA (see EBay item# 141931549970) and CCA (see EBay item# 142495590237). It connects easily with .25" fastons and needs only 4 connections; 12V, ground, signal-in and signal-out. It's epoxy-sealed into a standard relay housing, so it mounts almost anywhere. It's also waterproof, vibration-proof, and withstands temperatures to 250F. It comes with a 90-day warranty plus free email tech support if you need it. If you're presently using products like the MSD 8920, we think you'll find our BTAC2 is a superior alternative, providing higher boost output in a smaller, more convenient package. NEW! If you're a professional doing frequent engine or ignition swaps, these boosters are now available in lots of 5 at significant savings. See our listing# 143424727867. Note: Mounting Tab location may vary from position shown.