The 312B-3/4/5 accessory range for the Collins S-Line and KWM-2 transceivers
THE 312B-3 SPEAKER
This is the 312B-3 loudspeaker unit for use with the S-line/KWM-2. Surprisingly it has become quite scarce and attracts prices that approach that of the much more useful 312B-4 console described below.
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THE 312B-4 STATION CONSOLE
This unit contains a directional coupler for powers up to 2kW, phone patch connections and circuitry and a loudspeaker. It makes a very useful addition to any S-Line or KWM-2 setup.
Rear View
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THE 312B-5 CONSOLE/VFO
The ultimate accessory for the KWM-2/2A. In addition to all the facilities of the 312B-4, this unit is fitted with a 70K-2 VFO, which permits split mode operation with the transceiver. Interestingly, this affords greater flexibility than the 75S/32S combination as either VFO may be used for transceive. This means that the listening frequency may be monitored during split mode operations.
Illustrated here are two units, the one on the left is an early one, serial no 384 (Thank you Mr Krize!), and that on the right serial no 17533. Apart from the round emblem on the later model, the only difference I can determine is the lack of a finger hole on the tuning knob of the earlier version. They sure got everything right from the start on this one!
Rear views 
The 312B-5 is now quite scarce and commands a high price, but if you have a KWM-2/2A, it is a magnificent addition. The VFO is very stable, demonstrating once again that Collins maintained high quality standards during all production eras.