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About the T4B Unit

Here is a close-up of an early T4B unit. This one uses two Clairex CL-505L glass-encapsulated photocells and a Clairex CL-705 photocell housed in a gold metal TO-5 can. The cell on the right is used for audio attenuation and the cell on the left is used for gain reduction metering. The CL-705 is wired in parallel with the audio cell. I've always wondered about the purpose of the different colored stripes painted on the back of the CL-505s, and the hand-written numbers inscribed within each colored band.

Another view of early T4B construction. This view highlights the quality work and precision positioning of the heatshrink tubing used to make sure the photocell leads don't short out against the clamps holding them in place.

A view of the back of the early T4B circuit board, revealing that early units were hand soldered and they didn't bother to remove the excess flux from around the solder joints. The number 11202 must be the Teletronix part number for the circuit board. It's also interesting to note that the electroluminscent panel is held down by a piece of wax-impregnated thread, since this unit was produced well before the invention of the nylon wire tie.