[telephone related question]

any modern telephone has 4 diodes at its input i knowthat these diodes are for polarity protection but voice signals into or out of telephone are pass through these diodes how these signals are affected  are they rectified, i know that they are not rectified  are they carried over a DC level that enable them to fully pass, please i need an explenation about this point, thanks.

[Telephone: ELECOM INC. phonerex 9151]

please I need a schematic digram of a telephone: ELECOM INC. phonerex 9151
thanks.

[Understanding this circuit diagram of AK-700 telephone]

hi i have an extra equestion
can anyone tell me about how the signal pass from MIC through C7 to first amplification stage Q4 then passing small part of this signal to speaker through Q5, now how this signal reach the telephone lines to the caller side, how it pass Q2 and what about the rectifier bridge

[Understanding this circuit diagram of AK-700 telephone]

hi audioguru thank you very much for the useful informations u gave me and i have another questions as:
1- datasheets of hm9102
2- when someone talk near MIC, i think that voice signal  go through C7 to base Q4 then through the power line to the collector of Q2  at this point i cant understand, is Q2 is a common base amplifier or something else ..... what if Q2 is NPN type
3- i read that voltage between tip and ring lines is 48VDC, why they are 8.3 VDC at point A in the schematic.
4-is Q2 function as a pass transistor regulator inaddition to its function as a control device 

[Understanding this circuit diagram of AK-700 telephone]

hi friends my name is walid from Gaza strip, first of all I am new in this great website and 50% in English language and love passionately electronics. I am interesting in circuit design analysis than build it i think that if u understand u assurance can build so i want to understand the circuit diagram of AK-700 telephone from:
http://www.electronickits.com/kit/complete/tele/ak-700.pdf
especially Q2, Q3 and related components i want a detailed discussion about each element in the circuit, i go to many many websites for help and back to some textbooks and asking some people but no results.
Please someone help me, thanks.
[c:ak-700.jpg/img]