atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems 2600Hz Trunk Using Tellabs Cards

Hello all,

I'm posting this in the 1A2 area as this question involves tech that you guys would have at some point encountered in the days of the Bell System when things were still on in-band MF/SF for inter-office communication, and 2600Hz signifying an idle trunk/hookswitch flash/answer supervision.


As for my questions:

A phone friend of mine has two Tellabs cards tied together in a what I'm assuming is a loopback fashion that allows him to essentially add the famous old "cacheep" to his phone line on disconnect or hookswitch flash. I'd like to do this myself. Here is a link to the Tellabs module. Are any of you familiar in what way I would need to link two of these cards (he also mentioned he had a ring generator in there somewhere) together to make this happen? I also know that I'll need a 48V power supply to power these modules. Please forgive my geeky desire for something so trivial, but I wasn't around to listen to the magical ways of the old network. So this stuff is what brings a sparkle to my eye, and gives me a chance to play with what I wasn't around to see.

As always, any and all help/input is appreciated.

Scott

Well, I'm not sure what a "cacheep" is, so I'm not sure what he's doing.

The unit looks to be a 4 wire to 2 wire converter. We used these things when we had a 4 wire (usually E&M) circuit going to a location and wanted to put a 2 wire circuit across it. 4 wire circuits offered greater fidelity then 2 wire and were in common use in private and public networks. Your standard telephone is a 4 wire device (See the handset - 2 wires for transmit, 2 for receive) that is converted into a 2 wire device by the network in the phone.

I remember a time at the Bank....Our valued customer wanted a ring down (hot line) circuit between NYC and a facility they had in Utica. Of course they didn't want to pay for a leased line, nor did they want a dial up circuit.

The Data department had a T-3 that ran to Utica and offered us a channel on it, but the only available voice circuits were 4 wire. We used one of these cards at each end and fed a hot line circuit out of the PBX into it. It worked fine and may still be working yet. who knows?

I may have a 48v power supply. I'll look. You may need a ring generator too (I'm pretty sure I have one of those) and you will definitely need a tellabs card rack. These cards WILL NOT fit into a 1A2 card slot.

Sam

A bunch of the guys on C*NET are doing Asterisk-based MF send/receive with 2600 cheep. Check the archives over there for "MF Project."

Thanks for the offer, but I already have a ring generator and I've just purchased a Tellabs 24VDC/48VDC power supply, so I'm covered in that department.

I'm on the phone with him as I type this, this is the gist of what he said:

- You need an FXO and FXS card.
- TX from FXO to RX on FXS and vice versa.
- Ring generator goes to FXS.
- Apply -48VDC to both cards.
- As for connecting the line itself, on the pinout sheet there is a connection for the T/R on the FXO card. Phone connects to the FXS T/R.
- Adjust the dB levels accordingly using the dip switches.

As for the "cacheep," I'm referring to the burst of 2600Hz that comes over the line when the called party disconnects or flashes the hookswitch.

Scott

Arthur... I can always count on you to remind me what I completely forgot about. I forget about Asterisk's capabilities sometimes. I may just go that route instead, but I'm certainly interested in everyone's input on this.

Ah! "Cacheep". Now I understand....

FXO = Foreign Exchange Office. In other words, you're getting service from a "foreign" (not your own) switch. Office= the side that goes by the switch, or the far end.

FXS= Foreign Exchange Station. Station side is the local (near) end of the circuit.

Don't forget the card rack to hold these critters or you'll be soldering wires on and making a god awful mess.

Sam

It's the sound that you hear at the end of Pink Floyd's song "Young Lust" (A.K.A: Dirty Woman), where the guy keeps calling a number in England and the girl's boyfriend keeps hanging up. Classic operator intervention and international calling tones and sequences back in the 70s.

'Cha deep cheep'

Aha. Now I know what it is...thanks Ed!