The CDO's

Historically speaking, in the 1950s and 1960s the small towns surrounding Omaha in Douglas and Sarpy counties had local dial service, but very limited local calling areas. These communities were served by 'Community Dial Offices' consisting of smaller direct-control Step-By-Step (Strowger) facilities. These typically served anywhere from a few hundred to a few thousand subscribers.

The switches in these offices were typically configured to allow 'permissive' 5 or 7 digit dialing. For a call within the office, the full seven-digit number could be dialed, but only the last five digits were actually required. 'Digit absorbing' first selectors in these offices permitted dialing plans such as this.

Party lines were very common in these offices until the 1970s, with the far rural areas having availability of four-party fully-selective service (ringer is silent except for calls to that particular subscriber) if they were lucky, but often times eight-party semi-selective (one long ring or two short) service only.

Ma Bell chose to avoid the frequency-selective ringers used by independent telcos which allowed fully-selective ringing for up to 12 parties on a single line. Instead they chose a system where the ringing voltage was applied to either one conductor or the other, in either a positive or negative polarity, giving four possible fully-selective combinations. To service eight parties, one-long and two-short ringer cadences were used.

The advent of Subscriber Carrier ('AML') in the late 1960s provided some relief for far rural subscribers, but the result was often that one lucky subscriber on each rural line received a private line, while all others were stuck with eight-party semi-selective service.

Bare copper open-wire lines, supported on wooden crossarms with glass insulators were still in use into the 1970s. As these were upgraded to either multi-conductor aerial or underground lines, the availability of single-party private lines became common in rural areas.

Around 1970, several nearby communities with existing CDO's were integrated into Omaha's toll-free local calling area. This made significant use of the 19th. St. Crossbar Tandem office. As phone 'enthusiasts' know, Step offices do not easily interface directly with Panel and some #1 Crossbar offices, making either a tandem office or a toll office a necessity to provide direct dial service between them.

Calls from metropolitan Omaha to these extended-area offices required the usual seven digits, and except in a very few cases, these calls were routed through the Crossbar Tandem. The outpulsing of dial pulses from the Crossbar Tandem to the Step CDO was clearly audible after dialing was finished.

Calls from these CDO's to Omaha numbers or other CDO's required the dialing of an access code, usually 5 or 7, in addition to the seven-digit number. The dialing of this access code caused the first selector in the CDO to seize a trunk to the downtown Tandem's dial-pulse receiver.

One-plus Direct Distance Dialing from these offices was available, but DDD calls were routed to a 'CAMA Intercept' operator to verify and record the calling number, since automatic number identification of the calling number was not possible with the Step type CDO equipment.

Trunking from the Tandem to the CDOs at the time used analog medium-haul trunks with hissy analog repeaters, and background noise and 'singing' on calls to and between these offices was not uncommon.

In the mid 1970s, these offices were converted one by one to smaller WECO ESS units, but it most cases the calls were still routed via the 19th. St. Tandem.

Although calls to metropolitan Omaha (including Carter Lake) were toll-free, calls to Council Bluffs were long-distance to and from these communities until the 1990s.

• Elkhorn and Waterloo
  
  Originally, Elkhorn and Waterloo, neighboring communities separated by the Elkhorn River, each had their own local Step CDO. These were combined just prior to the extended calling area, resulting in the Elkhorn office serving both the 289 and 779 prefixes.
  
  An access code of 5 was required to dial numbers other than Elkhorn or Waterloo.
  
  Although residents of Elkhorn continued to be assigned 289 numbers, and residents of Waterloo continued to be assigned 779 numbers, the prefix codes were interchangeable and 'aliased' to each other as long as the office remained on the Step equipment.
  
  Due to the aliasing, the digit absorbtion, and the tandem connection, a local call from a 289/779 number to another could be dialed with 9 plus the last four digits, either 289 or 779 and the last four digits, or 5 plus either 289 or 779 and the last four digits.
  
  The Elkhorn CDO was cut to a #2 ESS around 1975. Some subscribers expressed dismay at losing the 5-digit 'shortcut' for Elkhorn and Waterloo calls. At this time 289 and 779 became discrete offices.
  
  
• Bennington
  
  The Bennington CDO had a very large service area but only a few hundred subscribers in the Step CDO days, including the town of Elk City, and extending as far north as some parts of Washington County, including the unincorporated community of Washington.
  
  Only two levels of the 238 prefix were actually in service, with the 9000 level aliased to the 2000 level, allowing for only 1000 total lines.
  
  It was rumored, but not substantiated, that Ma Bell put the Bennington CO and facilities up for sale to another telco during the 1990s.
  
  An access code of 7 was required for calls to other communities.
  
  
• Valley
  
  The Valley CDO was the most northwest in Douglas County, but the service area extended far south to the communities of Two Rivers and Venice.
  
  Several auto dealers in Fremont subscribed to FX service out of Valley to provide flat-rate toll-free service from Omaha customers, prior to the inclusion of Fremont in the Omaha toll-free calling area.
  
  The Valley CDO hosted the 359 prefix.
  
  An access code of 7 was required for calls to other offices.
  
  
• Springfield
  
  Springfield was the smallest of the CDOs with only the 2000 and 9000 levels provisioned, again aliased to each other. An access code of 7 was required for calls to other offices.
  
  A somewhat controversial decision by the Ma Bell powers that be was to cable the upstart community of Hawaiian Village, literally a stone's throw away from Springfield, to the far-more-distant 84th. and Harrison office.
  
  The Springfield CDO hosted the 253 prefix.
  
  
• Gretna
  
  The Gretna CDO had the distinction of hosting the most distant local calls from metropolitan Omaha, those being in the Linoma Beach and Beaconview communities, halfway between downtown Omaha and Lincoln.
  
  During the Step days, an access code of 7 was required for calls to other offices.
  
  The Gretna office hosted the 332 prefix. Due the similarity of 332 to other west Omaha prefixes, this was sometimes perceived as being 'more urban' than the other CDO's.
  
  

All of these CDO's were converted to ESS in the mid 1970s, allowing for Touch-Tone and various calling features, but toll-free calling to and from Council Bluffs would not come for another two decades.