I thought it would be fun to have a phone network wherever I’m living, for data and voice to different rooms and devices. There is tons of interesting communications history that is entangled with telegraph and telephony and this is a fun way to explore it.
I don’t remember having dial-up at home but we must have had it before DSL came around, as I remember using it to login to AOL at my friend’s house across the way. That was also the only place I remember using Windows Vista, we luckily stayed with XP until my parents stopped using their home computer.
I also have fond memories of staying at the motorbike shop my Mum ran, when she was looking after me. In the workshop they had a DOS machine that ran a custom DVLA MOT program, used dial-up and had a dot-matrix printer to print off the MOT certificates. Then up in the shop, there was an 95 or 98 machine with a stock/bookkeeping DOS program. She still runs the shop and although the workshop has upgraded to whatever new DVLA program on a modern machine, the shop runs the same DOS program through DOSBox.
Samsung iDCS 100
Without a ridiculously expensive telephone line simulator, a custom circuit providing ring/line voltages or using ATAs, I thought a surplus PBX would be the cheapest way to obtain a small telephone network. The ATA would restrict me to only a few devices without LAN tunnelling but these small-business PBXs can scale to tens of different lines, with multiple external trunks. Unfortunately, the documentation on these things can be quite skint.
I found a Samsung iDCS 100 (OfficeServ 100) PBX, in working condition.
{Front of the Samsung iDCS 100}
OfficeServ 100 Manuals:
The unit has the following cards:
- MEM - program memory card
- 2SLI - Standard analogue telephone line
- 2x 2BRI <– Without a PLL card, these BR/IDSN cards won’t work
{Interior view of the unit, with the 2x 2BRIs removed. Without the PLL card, these stopped the unit from booting normally}
The 2SLI card supports pulse/tone dialling and has long-line protection which should be interesting if I move somewhere rural. Without a 8SLI card, this limits me to only two full fledged analogue lines but it should be enough to get me started with modems with handsets on these plus another load of digital handsets for intercom use on the digital line interfaces.
Programming
This was a pain and in general is not well explained in the manuals. There are three main ways you can program the system:
- Serial - If a MISC card is installed you can program via a serial interface (local or remotely over a phone line)
- WAN/LAN - Using the corresponding cards
- DLI - This is the only method usable on my unit and any other stock iDCS 100. Using a digital handset connected to a DLI port, different `programs’ can be run and settings changed.
Luckily, these handsets are cheap and the unit supports a large number as standard. I bought a cheap DS-5007S and have used that to configure my unit.
The unit has no RJ11 or BT ports like other PBXs, instead relying on a patch/distribution board, which is connected to the unit by the two large 50-pin Amphenol/Centronics RJ21X connectors. I don’t have these so I broke out two SLI and two DLI ports with a regular CAT cable. I breakout board would be something I could design later on to make this a bit more permanent. That, or find an expensive RJ21X cable and patch panel.
frog
I’ve got the PBX working with my two phones and modem. The frog phone’s pulse dialling appears to broken and I believe an output transistor is the cause, as the pulse-dial IC is generating the pulses fine. I’ll need to check into this but I know pulse dialling itself works with the PBX as the modem can dial out fine.
{56K Modem, frog phone and DS-5007S}