My most recent project was to convert a newly acquired Hitachi SelecSet 700 for home use. This phone was given to me by my grandfather when his company replaced their much outdated Hitachi PBX with a new Mitel IP system.
This phone is proprietary for the PBX system, so I knew the phone would not work if I just plain old plugged it into the wall plug. I opened up the phone, and over the course of at least an hour, painstakingly removed the circuit board, keeping the inside of the phone in good condition. I cut the speaker and microphone leads from the circuit board and left them in their original positions so I could re-use them.
I then took a regular single-line General Electric speaker phone from my "phone vault," a.k.a. my closet, and opened it up. I removed the speaker and microphone, but left the wires and ran them out through a small gap above the handset plug. I ran some regular copper phone wire and connected the SelecSet's speaker and microphone to the proper wires from the GE phone.
I gave the speaker a test, and I received a nice, crisp sounding dial tone. I did a test call to my cell phone using the control phone's dial pad, which was successful. The microphone on SelecSet was surprisingly good! Sadly, even with the speaker volume level on the GE phone all the way up, the volume is relatively quiet. The handset, which sits on the SelecSet's cradle works flawlessly with good volume and mic output.
If you have any questions about this project, please feel free to send me a private message if you are a member of the Sundance forum, or email via this website by completing the form on the "Contact Me" page. Below I've included some pictures of the SelecSet. Thanks for viewing!