On 21 Jan 2006, at 16:02, Ian Stirling wrote:
The 1K resistors are not quite adequate protection on the input of IC1A.
I agree, and I would use 4k7 resistors here.
Four diodes, one each between the tip/ring connections, and VCC/ ground would be a good idea. 1N4148 or similar would be fine.
Or a chip diode pack.
And "SLEAVE" should be "SLEEVE".
-J.