See the attachment...
http://www.postimage.org/image.php?v=PqO6sj9

It presents switching of 2 sources using CMOS CD4016 Analog Switch into a single channel.

My question is, how can I switch 4 sources using a 'single clock'.

Here is my 'complex' interpretation,
Use clock to run one mod-4 asynchronous counter with outputs Q0, Q1.
Then construct one 'logic circuit' to drive 4016 according to the truth table given in the

attachment.

Can anybody suggests some easy tricks ?

 

That would work. Look into the CD4017 or CD4022 for your counter.
/mike

 

Depending on your sources, you would want to replace the 4016 with a 4066. The 4066 has the same functions, but is somewhat improved over the 4016.

 

Either use 4 outputs from a 4017, as suggested by n1ist, with each output driving an individual 4016 switch (or better still a 4066 as beenthere suggests).

If you do use a binary counter, just use a 4051 instead of a 4066. That will allow you to select up to one of eight inputs, with just a 3 bit address. no further address decoding 'logic' required.