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AEC-BOX-8/18/28 Literature
BRIEF: These devices are simple, fast and low cost LTC and / or VITC time code generators. The AEC-BOX-8, AEC-BOX-18 and AEC-BOX-28 models are no longer available.

Photo - AEC-BOX-28 - Standalone VITC/LTC Generator

The AEC-BOX-8/18/28 products were designed to provide you with fast, simple, and low cost generation of LTC and/or VITC signals.

The starting time, user, and embedded bits all default to "0", or can be set to any numbers you desire via EPROM changes either in the field or (for $20) prior to shipment. The default video lines onto which VITC is added are 14 and 16. These VITC line numbers can be changed via the EPROM or by internal switches.

Each box can be used with both NTSC and PAL video signals. The box automatically detects the incoming video standard and behaves accordingly. Thus a single box may serve ALL of your time code generator needs, both for now and for the foreseeable future.

If your application requires something a little different from what you see here, please give us a call. These boxes (and their software) have been designed with customization in mind. Since we are a small company, we can (usually) respond quickly to your particular needs, and at a reasonable price.

Related products include our PC-LTC, PC-VITC, and PC-VLTC families of internal LTC/VITC reader/generator boards for IBM PC/XT/AT personal computers (if slots are available), and our AEC-BOX-1/2/10/20 LTC/VITC reader boxes with RS232/RS422 serial interfaces.

Below you will find information to aid you in selecting the right AEC-BOX-8/18/28 time code generator to meet your needs. Please call us at 1-800-782-2321, or at the number above, if you have any questions. We look forward to hearing from you.


Tracey Ruesch, President

Adrienne, AEC, AEC-BOX, PC-207M, PC-LTC, PC-VITC, and PC-VLTC are trademarks of Adrienne Electronics Corporation. SMPTE is a trademark of the Society of Motion Picture and Television Engineers, Inc. IBM, IBM PC, IBM PC/XT, and IBM PC/AT are trademarks of International Business Machines Corporation.


Time Code assigns to each video frame (picture) a unique number, having the format Hours:Minutes:Seconds:Frames. This number may then be used for editing and/or control purposes. Each time code "frame" actually includes the time bits (just mentioned), 32 "user" bits (for tape ID's, etc.), and 6 more special "embedded" bits, such as the SMPTE drop frame (DF/NDF) flag. Time code standards have been around for many years, and are sponsored by both SMPTE (for NTSC systems) and the EBU (for PAL systems).

Vertical Interval Time Code (VITC) is typically present on two nonadjacent lines in the vertical interval (non visible portion) of a video signal. Longitudinal Time Code (LTC) is a specialized audio signal which is usually recorded on a video tape next to its associated video signal, but may also be used in an audio only environment.

The use of VITC frees up one audio track for other purposes, such as stereo audio. It also allows time code to be read at very low (including still) tape speeds, where fine positioning is important. However VITC cannot usually be read at tape speeds much above play speed.

LTC is commonly used because it is lower cost than VITC, can be added to a video tape after the initial video recording, and it can be read during high shuttle speeds (fast forward and rewind). However, due to record/playback limitations of tape machines, LTC cannot be read reliably at very low tape speeds.

In many cases both LTC and VITC are used at the same time, because of the advantages each has to offer.


As soon as an AEC-BOX-8/18/28 is turned on, it automatically starts generating LTC/VITC using the internal switch and EPROM settings as a starting point. Thereafter, the time bits are automatically incremented every frame, coasting through dropouts if needed. Two external TTL/CMOS/O.C. logic inputs (or switch closures to ground) allow the generator time to either 1) be held at its current value, or 2) reset to 00:00:00:00.

The front panel power LED will blink off if the video sync input is missing, or if any video sync errors are detected. Otherwise you will know that everything is hooked up and operating properly.

Because our boxes cannot detect color subcarrier phase, they are presently not capable of generating color framed time codes.

In cases where NTSC/SMPTE drop frame time codes are desired, an internal switch can be set to modify the box accordingly.


The VITC generator circuitry uses a proprietary IC to add VITC to the video signal which is currently being looped through the box. The time bits, video field ID bit, and the CRC byte are updated automatically every video field.

In the event that a video dropout is detected, the generator will "coast" along, incrementing the time code count as needed until the video signal returns.

Note that the VITC generator is actually an ADDER, which means that the line onto which VITC is to be added MUST BE BLANK. If a VITC signal has already been recorded on the desired line, you will have to find some other line. Also note that VITC cannot be added to the video signal on an existing video tape - it must be ADDED during original recording or while dubbing to another tape.

The "VITC ADD" output uses two standard BNC connectors, hard wired together, so that you can easily loop your video signal through our box. Attenuation is less than 0.1dB out to 5MHz.


The LTC generator will quickly and automatically lock to the incoming video sync signal. In the event that a video dropout is detected, the LTC generator output will "coast" for as long as needed, then smoothly slide back into alignment when the video sync signal returns.

In cases where no video sync input is detected, the LTC generator will freerun with about 0.1% maximum frequency error. Also, since in this case the box has no way of knowing whether a 25fps (EBU) or 30fps (SMPTE) LTC signal is desired, an internal switch determines the proper (default) frame rate.

The "LTC OUT" output is 1Vpp, low impedance (< 100 ohms), and has sloped rising and falling edges per the SMPTE standard. A standard RCA jack is used for this "audio" output.


AEC-BOX time code generators are packaged in small (modem sized), rugged (all metal), and attractive standalone enclosures. For better reliability, and for your convenience, each box has its own internal power supply, for which 115VAC/230VAC is required. Also, each power supply is Hi-Pot tested for everyone's safety.


Model       Description                                     Price
AEC-BOX-8   LTC Generator with Video Sync Input ............. 345
            Generates DF/NDF play speed LTC
            locked to the video input (if present).
            Otherwise freeruns using internal crystal.
            Auto NTSC/SMPTE and PAL/EBU detection.
AEC-BOX-18  VITC Generator (Adder) .......................... 345
            Adds DF/NDF VITC to "black" vertical interval
            lines present at the Hi-Z looping BNC's.
            Switch selectable VITC line numbers.
            Auto NTSC/SMPTE and PAL/EBU detection.
AEC-BOX-28  Simultaneous LTC/VITC Generator ................. 445
            Combines all features of BOX-8 and BOX-18
            for simultaneous generation of LTC and VITC.
Each box comes with a good instruction manual, schematics, 115VAC 
internal power supply, connector kit, and a 2 year warranty.
230VAC      Converts internal power supply to 230VAC .......... 0
REPROM      Changes EPROM default settings (specify) ......... 20
BNC2RCA     Adapter from BNC cable to RCA jack ................ 6
AEC-BOX is a trademark of Adrienne Electronics Corporation.
Prices subject to change without notice.     (C) January 1997 AEC
                         Made in U.S.A.
Copyright 2006 Adrienne Electronics Corporation
Last modified: 02/22/13