Staigen

I also have a few sugestions for this circuit, but also a warning. First i sugest that you bypass the diodes D1 to D4 with a couple oh caps, about 1nF to 4.7 nF, soldered directly over the diodes. Also bypass diode D7 with a cap, lets say 10 MFD to 47 MFD. The supply to the IC:s should also be bypassed with a ceramic cap, about 100 nF. And so the warning, how about the SOA(Safe Operating Area) of the output pass transistor Q4? //Staigen

Here is version 1.0 : ExpressSCH_Components_V1.0.zip

I have designed a few components for the ExpressSCH. Maybe somthing for others to share? Can I upload it to you, or shall i send a link to my homepage? //Staigen

The forum at Techlib.com is back again! Urls: Techlib.com: http://www.techlib.com/ The forum: http://www.techlib.com/disc5_frm.htm //Staigen

Oops! I forgot, its a monitor :o ::) //Staigen

I need a Service Manual or shema for a Hewlett Packard Ergo 1024 Model D2831A //Staigen

Ok, BTW, you can connect the transformer directly to the phone line via a relay or something, thats the way modems are connected. //Staigen

Ok, i am not so good at the english language, but you did not answer the question! And its transmitter, not transmiter //Staigen

I know what DTMF is, i have known it for about 30 years now, what i was curious about was what a TRANCIEVER is used to //Staigen

What is a DTMF tranciever used to? Just curious! //Staigen

Hi there Mozikluv, if C3/R7 is connected to pin 6 of U2 the signal goes to the +(noninverting) input of U2 and the amp acts as a second order lowpass filter (like it says i the text), and if C3/R7 is not connected to pin 6 then i belive its a allpass filter with a little dip at the resonance frequency and some reduced output in the high passband! There is also somthing else that i dont like with this schematic, regarding the U5 opamp, it is not properly biased.

I belive there is a little drawing error at U2. C3 and R7 shall be connected to pin 6 on U2.