This is an extract from
http://www.infectionmusic.com/arpodyssey/Synth%20Manuals/Arp2600-FundamentalsOfMusicTechnology.pdfTHE ELECTRONIC SWITCH
The electronic switch is one of the most unique and oft forgotten parts of the 2600. It consists entirely
of three jacks labeled A, B, and C. The electronic switch alternately connects jack C to jack A and jack
B. When A is connected to C, B is disconnected from C, and vise versa.
The internal clock is permanently normalled to the electronic switch, and determines the electronic
switch’s rate of switching. One may recall that the internal clock was described as putting out a series
of trigger pulses which drive a square wave oscillator, and it is this square wave which drives the
electronic switch. The 2600’s designers thoughtfully indicated this with a rather long square wave next
to the line indicating the internal clock’s normal to the electronic switch. (See Figure 10-2 on page 75.)
It is interesting to note that the electronic switch’s jacks are neither specifically inputs nor outputs. For
instance, one could connect the output of an oscillator to jack A, and it would come out jack C when the
electronic switch connected the two. One could also connect the output of an oscillator to jack C, and
the signal would alternate between coming out jack A and jack B. Thus, the electronic switch’s jacks
are either inputs or outputs, depending upon what is connected to them.
One may recall that by connecting a pulse wave to the EXT CLOCK IN jack, the rate at which the
sample-and-hold unit sampled could be determined by an external source. Again, the internal clock’s
normal to the electronic switch cannot be broken, and so the internal clock will always determine the
rate of switching. This is both useful and unfortunate. While it is wonderful to be able to make the
sample-and-hold unit sample at a rate which is independent of the electronic switch, it is unfortunate
that they cannot both be synchronized to an external source using the EXT CLOCK IN jack. Of course,
if the external source can be synchronized to the internal clock, this problem can be solved.
THE ELECTRONIC SWITCH IN PRACTICE
There are hundreds of potential uses for the electronic switch, only a few of which are presented here.
They basically fall into one of two categories: patches which use distribution and patches which use
source switching.
In the basic distribution patch, jack C is an input, and the incoming signal is alternately distributed to
jack A and jack B. One unique possibility with this configuration is a panning patch. If a sound source
such as an oscillator (or the VCF’s output, for that matter) is connected to jack C, and jacks A and B are
connected to the LEFT INPUT and RIGHT INPUT jacks in the mixer section, the sound coming into
jack C will be switched between the left and right speakers. This can be heard on CD track 51.
