Printed board assembly
Assembly is fairly easy. Be careful buying the BAT46W in the correct package. I've updated the PCB to revision /1, replacing the BAT46WJ (SOD-323) to BAT46WH (SOD-123). The -WH variant is bigger and easier to solder by hand.
Programming the board
I explained the procedure already in a previous log. To connect the programmer to your ATTINY85, you can use a Pomona SOIC-clip as shown on the image below.
Measuring interrupt frequency
To check if the crystal has the correct load capacitors attached. A special debug firmware is loaded into the device which generates a square wave with a frequency that should be 31.250KHz.
Mounting in the housing
The housing originally contained an ADSL-splitter. It can be bought for a few cents from AliExpress. Its PCB has been removed. The modular jacks have been transferred to the pulse-dtmf-converter.
The Philps DECT-phone, which uses tone dialing is connected to the "PHONE"-port of the converter, as indicated on the bottom of the housing.
The FXS-port of the internet gateway is connected to the "MODEM"-port.
The pulse dialing phone is connected to the "LINE"-port.
Making a few test calls assured me that both phones are working well.
That's all, folks.