Top Telephone Switches

With AT&T saying that “with each passing day, more and more communications services migrate to broadband and IP-based services, leaving the public switched telephone network (“PSTN”) and plain-old telephone service (“POTS”) as relics of a by-gone era,” I thought it would be a good time to get a snapshot of the North American telephone network as it exists now. In the early 1970s, phone phreaks like Evan Doorbell and Mark Bernay started recording what they saw as the demise of the electromechanical telephone network. The switches then were crossbars and panels and steps and the like, with early computerized switches like the 1ESS just starting to appear. Now, the 1ESS is nearly gone from the network, and the North American network consists mostly of the Western Electric/AT&T/Lucent/Alcatel 5ESS (the 1ESS’s successor), the Nortel DMS-10 and DMS-100, the GTE Automatic Electric GTD-5 EAX, and the Stromberg-Carlson/Siemens DCO. A few other switches in the network, like the Siemens EWSD and the Ericsson AXE 10 have found more popularity in North America as cellular switches (and as wireline switches in other countries).

The oddball switches are the ones that really interest me, and they’ll be the first ones to disappear from the network. I’ve been told that the TRW Vidar ITS-5 and the Mitel GX5000 switches may be gone from the North American network. To see what might be left, I decided to do some digging, and I’ve come up with a list of the telephone switches (minus remotes) still in use in the North American network. There’s undoubtedly some stale data in this database, and so for rare switches, I think the numbers listed are the upper boundary — the lower boundary may be as low as 0. The list also contains the mystery “Digital Switching System”. There seems to be an awfully large number of them for it to be the North Electric DSS-1, which became the ITT 1210 — maybe it just means “unknown digital switch”?

The picture above of the GTD-5 EAX was shamelessly stolen from the site of a GTD-5 consultant, the only place I could find a picture.

Top 10 Switches

Manufacturer Switch Count
NORTEL DMS 100 2513
LUCENT 5 ESS 2236
NORTEL DMS 10 1968
AUTOMATIC ELECTRIC GTD-5 EAX 668
SIEMENS DCO 522
  DIGITAL SWITCHING SYSTEM 247
REDCOM MDX 384 155
ERICSSON AXE 10 102
SIEMENS EWSD 91
LUCENT 1A ESS 66

The Whole List

Manufacturer Switch Count
NORTEL DMS 100 2513
LUCENT 5 ESS 2236
NORTEL DMS 10 1968
AUTOMATIC ELECTRIC GTD-5 EAX 668
SIEMENS DCO 522
  DIGITAL SWITCHING SYSTEM 247
REDCOM MDX 384 155
ERICSSON AXE 10 102
SIEMENS EWSD 91
LUCENT 1A ESS 66
MITEL CORP LTD GX5000 DIGITAL SWITCH 64
  PACKET END OFFICE 54
METASWITCH, INC. METASWITCH VP3510 28
NORTEL SA1 24
LUCENT 5ESS-2000 SWITCH 22
NORTEL DMS 200 21
SIEMENS DCO  21 18
METASWITCH, INC. METASWITCH VP3500 17
TEKELEC INC IX7000 (TM) NEXT GENERATION CLASS 5 SWITCH 16
REDCOM LABORATORIES MDX 10K (MODULAR DIGITAL EXCHANGE) 15
VIDAR ITS 5 14
METASWITCH, INC. METASWITCH VP2510 12
NORTEL CS 1500 12
TEKELEC INC OPEN COMPACT EXCHANGE (OCX) 12
  COMMUNITY DIAL OFFICE 12
CIT-ALCATEL INC E10 – FIVE SWITCHING SYSTEM 11
NORTEL DMS 500 11
SIEMENS CENTURY DCO6000 10
AUTOMATIC ELECTRIC STEP BY STEP 8
LUCENT 5ESS-2000 SWITCH VCDX 8
NEC CORPORATION OF AMERICA NEAX – 61 8
  9A ANNOUNCEMENT-WEATHER 8
  ANNOUNCEMENT SYSTEM 8
SIEMENS EMD55 7
LUCENT 4 ESS 6
SIEMENS XY 6
HARRIS CORPORATION RURAL ELECTRONIC EXCHANGE 5
NORTH ELECTRIC DSS 1 5
ALCATEL 1210 4
ALCATEL CRX 4
NEC NEAX – 61E 4
NORTH ELECTRIC DSS 4
SIEMENS DTM 4
TEKELEC INC 7000 CLASS 5 PACKET SWITCH (T7000) 4
ALCATEL 12 (HOST) 3
LUCENT 5ESS-2000 CDX (COMPACT DIGITAL EXCHANGE) 3
METASWITCH, INC. MG3510 3
SIEMENS DCOSE SMALL EXCHANGE 3
  4A ANNOUNCEMENT TIME 3
  CALL AGENT 3
VIDAR IMA2 3
ALCATEL A1 – SPC 2
METASWITCH, INC. METASWITCH VP3000 2
NORTH ELECTRIC CX 200 2
NORTH ELECTRIC NX2A 2
REDCOM LABORATORIES IGX-MT END OFFICE SWITCH 2
SANTERA SYSTEMS INC. SANTERAONE (BOX) BROADBAND OFFICE EXCHANGE 2
SIEMENS DCO  80 2
SIEMENS DCO 200 2
SIEMENS ESC(1) 2
  AUTOMATIC CALL DISTRIBUTOR 2
ALCATEL RELAYMATIC 1
AUTOMATIC ELECTRIC 375A 1
GLUON NETWORKS INC. CLX(TM) CONVERGED LOCAL EXCHANGE 1
ITEC INC EMS-1 1
LUCENT 1 ESS – 2WIRE 1
LUCENT 1 ESS – 4WIRE 1
LUCENT 1 ESS – HILO 1
LUCENT 2B ESS 1
LUCENT NO 5 CROSSBAR-4WIRE 1
LUCENT NO 5 CROSSBAR-ETS 1
LUCENT PLEXUS 9000 1
LUCENT STEP BY STEP 1
NORTEL CS 100 1
NORTEL DMS-10 AP 1
NORTEL DMS10 SIGNALLING RELAY POINT 1
NORTEL NO 5 CROSSBAR 1
NORTEL STEP BY STEP 1
NORTH ELECTRIC CX  30 1
ROCKWELL INTERNATIONAL ISS 3000 1
SIEMENS MAINSTREETXPRESS 36170 1
TEKELEC INC 9000 DISTRIBUTED SWITCHING SYSTEM (DDS) 1
  ANALOG SWITCHING SYSTEM 1
  CONCENTRATOR 1
  CROSSBAR SWITCHING SYSTEM 1
  PACKET SWITCH 1
  SWITCHED DIGITAL DATA SYSTEM 1
  LXP – 4 1
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10 Responses to Top Telephone Switches

  1. Robert Hyser says:

    I am a retired Telephone person, worked for Automatic Electric Genoa Ill and Northlake, Il. in sales and product development. I am interested or more curious about the LXP-4 analog switch you show as 1. Can you tell me the location please? LXP-4 LEICH CROSS POINT-4 TPS, was made up of the Cross Point Switch and all relays. They also manufactured the LEICH TPL system which was used by the GTE companies and REA for their small rural area magneto replacement, up to 400 lines comfortably. Although I do not know of any more in existance, there is still a complete system in a wharehouse that would like to find a home in a museum or the like. Anyway thanks for listening to me.
    Bob Hyser

  2. Robert Hyser says:

    see comments see above

  3. Bob Hyser says:

    Andy not sure if you want to add this to your list of switches since I think they are no longer any in service.
    GTE AE Brookville Canada made a fully stored common controll system called the C-1 EAx, there were a number of them sold with in the GTE system as well as Canadian TelCos. AE also made the following systems besides the SXS and GTD-5. #1 EAX CLASS 5 4/5, #2EAX STORED PROGRAM COMMON CONTROL SYSTEM CLASS 5 4/5; #3 EAX CLASS 3 ONLY NO LINES. THERE ARE OTHER MANUFACTURERS THAT WERE AROUND IN THE 50′s and 60′s not sure how many you want to add to your list. Any way have a good day and if I can be of any further service please contact me.
    Also as I mentioned, LEICH had other systms, LXP-2 and TPL all relay as well as the one shouwn LXP-4
    Bob Hyser

  4. W. A. Smith says:

    A question for Bob Hyser – I have seen reference to a switch called No. 1 XPT – Which
    looks like it might be called Number 1 Cross Point Tandem – Was this a GTE A.E. – switch – If it was when was it made – locations etc. Noticed your reference to the C1-EAX. I worked with the only C1-EAX PL-1 in Michigan during my time as a
    switchman for GTE/Verizon.

  5. ROBERT HYSER says:

    Andy The XPT was manufactured I believe in the 70′s. I have a good friend who was a designer back then that will knowe so I will contact him for more details. The XPT was a trunk to trunk switcher no lines. It was replaced by the #3EAX.
    Bob

  6. Larry Strickland says:

    The C1-EAX was a stored program control class 5 end-office switch. Was very advance for its time, original design was to provide metropolitan type service to remote rural customers.

    I taught numerous classes as employe with GTE of Ohio in the 1970′s for the C1-EAX maintenance employees.
    Larry Strickland

  7. Roy Latham says:

    I was on contract assignment to GTE International in 1978/9. We were installing #1EAX switches for class 4 & 5 operations in Teheran, Iran. They were the PL2 version with MOS memory and had a special modification that allowed the terminating markers to work simultaneously. Unfortunately, we didn’t get to see how well it worked as there was a little thing called a revolution that stopped any of them being put into service – except the Class 4 switch as Kushk-A. As far as I know they’re still sitting there ready to go once someone boots them up again and puts the trunk cards in them.

  8. Raymond Fiorini says:

    Hi,

    I was GTE’s first electronic engineer going from steo by step to the C-1 EAX switch. The C stood for it was made in the Brockville Canada plant . It was our first common control switch. It used a hexadecimal code for programming. The programming core consisted of ring magnets, a wire inside was a Zero and a wire outside was a One. It was a class 5 type office. I was the Engineer for the St. Petersburg Florida No.! EAX switch.. It was our first real common control switch that used regular programming. The program was loaded using a Mylar punched tape. Since it was our first electronic switch of any size, ?GTE of Florida was actually afraid of it. We had to develop what we called a chicken switch. It consisted of a battery of relays, so if the No.1 EAX failed they could turn on the chicken switch and convert the office back to the then existing SXS switch. WE never needed it. The program was stored on magnetic drums, that came from the computer industry. Basically it was a magnetic material like that on magnetic tape. It spun at 6000 rpm and had 500 heads to take the info off in a small time. It contained lots of electromechanical parts to provide featured and it was transistor, transistor technology. I also was the development engineer for the No, 2 Eax. It was our first switch to use coreeds instead of relays for line switching. It was more electronic than the No!. EAX in that features were provided by software, instead of electromechanical switching. The soft ware was loaded using magnetic tape in lieu of Mylar tape with holes punched into it.It used transistor small integrated circuit tehnologyThe soft ware was stored on MOS memory cards. What is missing is the GTE-120 switch. I taught that switch to operating companies. It had 120 lines and an attendant position, all housed in an aluminum suitcase. When I went to teach it, the engineers taught that the suitcase was my training materials. When I told them that I was carrying the entire switch they could not believe it. It had a small pack of Gates cells as backup batteries. Programming was done by a large tape cassette. It also has MOS memory. Then there was the GTE-1000, Which I also trained operating companies on its use and features. It consisted of 4 equipment frames and it serviced 1000 lines. Then there was the TSPS switch this was a electronic switch for operator positions. I am not too familiar how it worked I neither taught or engineered one. The GTE-120 and the GTE-1000 were business switches and not central office switches, I almost forgot about the GTD-5 switch it was a central office switch which could be used up to a class 4 office. it used large scale integrated technology and was a time based space switch.

  9. Raymond Fiorini says:

    Ray Latham worked with the Iranians, poor guy, my manager

    Roy Latham worked with the Iranians. My manager Tony Matchus from GTE was on assignment in Iran. These people were miserable to work with. In addition to the equipment we had to provide every thing like file cabinets for the specification sheets. We told them that it had two coats of paint on them and we had to give them proof that it was two coats. There customs were weird, We Pull our hands toward us if you want some one to come to you. Over there it meant for you to go away. My boss had a secretary and the first day he pulled out his lunch to eat. He then went down the hall to get a drink. When he came back his secretary was gone. There was only the one hall and she did not go by him. He even looked out the window to see if she jumped. When he finished eating she appeared out of the closet! Custom is you cannot eat in front of your boss. So I am not surprised if any of the 10 switches we sold to them are not working, they did not believe any thing we told them.

  10. Ken Gasbarri says:

    I signed on with GTE Automatic Electric as a “test engineer” to go to Iran for the #1 EAX, but on a Friday, two weeks into the school at North Lake, (and after the tornado) Wayne Wilson walked in to our classroom and asked for volunteers to go to Mahomet and install the first #2 EAX. I was one of the “volunteers” to be picked. Having Iran in the back of my mind, I was thinking Mahomet was somewhere in the Middle East, and was somewhat surprised when I was told to report first thing Monday morning. Anyway, Mahomet is a small town in Illinois.

    We arrived to find a small building full of frames and steel work still in the crates, and no manuals or instructions. We had a great bunch of installers as they had things up and assembled in short order. Then the fun began.

    Like the #1, the #2 used hexadecimal. A 16 bit address bus with a 32 bit data bus. But it did not have a ROM boot system. We had a thing called the X-ray Test Set. A large box with a lot of 98 pin connectors on the back, and two rows of toggle switches on the front. One row contained 16 switches for the address bus, the other had 32 switches for the data bus.

    If and when the system crashed, and it crashed a lot, someone would have to man the switches, while someone else read the (as I remember) 440 instructions required to operate the tape drive in order to load the program. The address bus started with all zeros, and incremented by one until we had all instructions loaded. We would toggle the address, then toggle the data for that particular address, then hit the “load” switch and go on to the next address. As you can imagine, if we got on bit in either the address or data bus wrong, it would not work, and we would have to start all over. We did manage to survive those early days until North Lake developed a boot program.

    We didn’t have the “chicken switches”, and the turn over was a do or die ordeal, but it went pretty smooth, with the only problems being a few lines that somehow didn’t get switched.

    We started having issues with the CPU at an early stage, and didn’t discover until later that the central office manager was warming his lunch on top of the CPU files, thus blocking the air flow and causing the system to overheat.

    Also, the previous switch was of course a Step switch. The local customers needed only dial 4 digits to make a local call, and were not very happy with the new technology because now they had to dial all 7 digits.

    I went on to work at switches in Fort Dodge, Iowa; Roseville California; Gresham, Oregon; The island of Oahu in Hawaii, and finally Texas.

    One final note. Years later, I was being interviewed for a job in Saudi Arabia to basically do the same thing. The interviewer was using a loose leaf book to find technical questions to ask. me. On one question, I answered as per the book, but mentioned that the correct answer was penciled in on the right margin. He was shocked that I knew that, but when I explained that I had pretty much written the book, he was quite impressed (wrongfully so). I didn’t take the job. My personality and the laws in Saudi Arabia just didn’t mesh well.

    Ken Gasbarri

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