+5v trigger for tap tempo

[mark scetta]

hi lists,

i am a novice to electronics (i'm building a MOTM modular...) and an avid
analog synth freak. i need help with the electrical specifics of building a
tap tempo trigger box that i will use to set the arpeggiator rate on my
Jupiter 6. here are the details:

the JP6 has a trigger in that will set the arpegg clock rate. it is designed
to get its pulse from a TB-303, putting out +5v. i would like to DIY
something that puts out this pulse *and* has a tap-tempo interface so that
when i tap it twice, it assumes that tempo. also it must have some kind of
bypass or on/off switch (for times when i'm not using the arpeggiator). i
think what i'm trying to build here
is a metronome of sorts, but i'm not versed enough in electronics to be able
to design it, especially the tap tempo part.

any help appreciated,
mark