Sony - WM-7 Walkman

DESCRIPTION
The first ever Walkman to have auto reverse and (basic) inline remote control unit. It is one of the most complex of all the Walkman models, and the only one model ever to be released with 3 motors. Only one motor is used for tape transport though.
With the WM-7 came several new functions: it was the first with full electronic (logic) controls, auto-reverse, Dolby B noise reduction and a "hold" function that blocked all the keys when set.

Except the tape transport motor, from the WM-2, the mechanical sections were all new. The brightly polished metal mechanism was highly complex yet sturdy. Two small DC motors operated the clutches and the head bridge, making remote control of the reverse and stop functions possible. Other refinements included magnetic take-up clutches and a bi-azimuth system: alignment of head separately for each playback direction. All modes are released when the door is opened. The auto reverse action is triggered by an optical sensor and can be set to play the cassette once only or continuously.

The designers used a DC-DC converter to step up the voltage, as with the TC-D5. The converter was bulky, so it was placed in a space next to the battery holder. This allowed the Walkman to be powered by 2 AA batteries only.

Operation was simple. Providing the safety switch was not set to "hold", pressing either of the two play keys would start the tape in the direction desired. Two LED indicators showed both the tape direction and the battery condition. Winding in either direction could be initiated instantly without damage as all movements were synchronised electronically.

The remote control was a "first" and worked using a special pair of headphones which contained a control unit in line with the cable. The stop and reverse functions could be triggered from this device. The system operated by open-circuiting either the left or the right headphone channel. Because of this, the WM-7 could only be used with an amplifier or loudspeaker system wit a special adaptor. Inserting or removing a regular 3.5mm jack will stop any operation.

The WM-7 introduced some new and interesting features, at the cost of massive complexity. It’s amazing how soon many of these features became available on lower cost, mid range models.