Rotary-dial phone with VoIP

Since a short time I am the proud owner of an old dial phone from the 70s. It is a “PTT 50 Tf3-39.205” from the company Zellweger Uster from 1972, which can only do the old pulse dialing.

PTT 50 Tf3-39.205

With pulse dialing, corresponding pulses are sent for each dialed number: 1 at 1, 9 at dialed 9 etc. By timing the pulses correctly, the telephone number to be dialed is transmitted in the process. In today’s era of technology, practically all landline telephones work via VoIP and only a few routers still support pulse dialing. More widely supported, on the other hand, is multi-frequency dialing.

Of course, my old phone doesn’t support VoIP or multi-frequency dialing, so I want to upgrade it with a VoIP gateway. The only compatible gateway I have found is the Grandstream HT801.

After converting the existing cable with eyelets to a normal RJ11 phone cable, connecting it, configuring the SIP login data of my phone number, and activating pulse dialing on the Grandstream, the phone works flawlessly!

Alternatively, an IWF-MWV converter can be used, but this is quite expensive (about 100 CHF). Due to lack of time, I could not try these OpenSource schemas and building instructions, but they look promising:
Note, however, that a gateway is still necessary. Mostly the Fritzbox can be used for this purpose.