Coin Telephone Introduction

Introduction

The purpose of this manual is to familiarize coin personnel with the many intricate phases of coin service.  This includes an overview of the total coin operation with emphasis on:

  1. Station equipment
  2. Central Office (CO) testing and circuit design requirements
  3. Trouble analysis of station, loop, and central office equipment
  4. Cord board and Traffic Services Position System (TSPS) operation
  5. Loop plant
  6. Coin improvement items including Dial Tone First

To understand and effectively clear troubles on coin service, a basic knowledge of the above items is necessary.

Coin service today, consists of Dial Tone First (DTF), Coin First (CF), and Post Pay type service.  All utilize the single-slot coin station and all place different demands upon central office and test desk equipment.

Prior to the development of the single-slot coin telephone and introduction of DTF service, coin operation was relatively simple.  The coin station (multi-slot) placed very few demands upon the central office and test desk equipment.  If the central office equipment could furnish a threshold capable of collecting or refunding a coin deposit, test for the presence of a coin, provide a minimum amount of talking battery, and ring the station ringer, the station performed quite effectively.

Social changes during the 1960s (whiny rich kids) made the multi-slot coin station a prime target for vandalism, strong arm robbery, fraud, and theft of service.  This brought about the introduction of the more rugged single-slot coin station and a new environment for coin service.

Presently there are four types of single-slot coin stations all having an identical outside appearance:

Components for the single-slot coin stations, although appearing the same and physically fitting the same mountings, are not always compatible.

The operational description of the single-slot coin station is explained in the following pages.  The operational description must be understood by the central office and test desk force maintaining coin service.  The station totalizer assembly as outlined next, affords a natural trouble indicator and trouble analyzer for loop plant, station, and central office trouble conditions.  The Master Test Frame (MTF), maintenance control center, district junctor test frame, J-test boxes, and coin supervisory test sets are good test facilities, but lack the trouble detecting features that the coin station totalizer provides.


General System Considerations for DTF Conversion

Station Compatibility

The operational description for the "A" series coin station is similar to that of the "C" series station wired in the CF mode.  The difference being - the "A" series coin station requires that talking battery always be negative to the ring side of the line with ground on the tip side.  The "A" series station therefore, will not operate with office or loop condition when reversals are present.  In central offices providing both DTF and CF type service it becomes necessary to modify the "A" series stations to "C" series.

With closing of cord boards and implementation of TSPS, personnel involved in coin service must be aware of the polarity sensitivity of the "A" series coin station.

Polarity Reversal Examples:

  1. The trunks to TSPS provide +48 VDC talking battery on the ring side of the line when serving DTF service.  This is deposit recognization for less than initial rate and also utilized to prevent Touch-Tone® fraud (fraudulent simulation of coin signals by manipulating Touch-Tone® dial buttons).
  2. Toll diversion option on No. 5 Crossbar trunks to TSPS reverses the talking battery.
  3. In Step-by-Step offices polarity reversals may be experienced due to malfunction of switching operations or local calls completed to a coin station.

The above examples will render the "A" series coin station out-of-service.

The following items are of a general nature and pertain to all switching systems.  It should be noted that they are not listed in any particular order relating to their importance or urgency, but are considerations in converting an existing central office to DTF coin operation.

Cutover Coordination

Conversion of offices to DTF operation requires coordination of the central office and station changes if unimpaired coin telephone service is to be maintained during cutover.  Cutover to DTF coin operation can cause customer confusion.  This confusion is compounded when temporary incompatibilities are introduced between the central office and coin telephones by the cutover procedures used.  The central office serving arrangements permit side-by-side operation of CF and DTF stations without line segregation during and following cutover.  However, full cutover of all coin telephones to DTF operation in a local central office will allow the customer to more rapidly learn the new method of operation without need to identify the type of station (coin first or dial tone first) which he is trying to use.

Cutover Procedures

The following DTF cutover procedure has been used by serveral companies with minimal impact of the cutover (other than customer unfamiliarity with the new service) on coin telephone operations.

  1. Modify  Test desk, test cabinets, test sets.
  2. Modify  CO equipment with the exception of +48 VDC options.
  3. Modify or Change  Stations to "C" series.
  4. Modify  Toll equipment with the exception of +48 VDC options.
  5. Prepare announcement circuits and announcements.
  6. Implement +48 VDC options.
  7. Test all circuits using a "C" series coin station wired in the DTF mode.
  8. Convert  Line relays to loop start.
  9. Convert  Stations to the DTF mode.
  10. Change  Dial instruction cards.
  11. Make final test of station in DTF mode.
  12. Make final test of all associated CO, toll, test desk equipment.
  13. Make final check of announcements.

Deposit Required Announcement

The standard announcement that is recommended for use when the required initial rate coin deposit has not been detected is as follows: "The call you have made requires a 10 cent (initial rate) deposit.  Please hang up, wait for dial tone, deposit 10 cents (initial rate) and dial your call again."  In addition, when all announcement trunks are busy during heavy traffic conditions, calls should be routed to recorder tone.  Routing to another recording can only confuse the customer.

Coin Present Tests

Coin present tests prior to coin return on abandoned calls and coin disposal tests to determine successful coin collect or coin return actions must be made using positive (+48 VDC) battery.  Coin deposits of less than the initial rate will not be detected by a negative battery test (-48 VDC), since the unoperated initial rate contact (T1) at the station will prevent coin ground detection.

Subscriber Line Multiplex (SLM) Operation

The SLM has been arranged to serve CF coin telephones.  It cannot serve DTF or CF coin telephones in a DTF equipped office.  Alternative facilities must be provided for all SLM coin lines when the office is cutover to DTF operation.

Talking Battery Polarity on Operator Trunks

As covered in the various letters, +48 VDC battery is necessary at the DTF wired coin telephone when an operator is monitoring coin deposits.  Unless the trunk provides this polarity, the operator will be unable to monitor initial deposits which are less than the local call initial rate (5 cents in 10 cent areas, 5 cents and 10 cents in 15 cent areas and 5 cents, 10 cents and 15 cents in 20 cent areas).  This requirement covers trunks which handle terminating traffic requiring coin deposits at the coin telephone, i.e., collect calls to coin telephones as well as trunks handling originating traffic.

Toll Grade Battery

The coin service improvement program which initiated DTF service included option changes in central office circuitry to eliminate toll grade battery.  The low impedance presented by this supply can result in currents at the coin station (on short loops) in excess of 200 mA which limits the design options for new station circuitry.  All circuits which supply toll grade battery toward the station should therefore be modified per the appropriate drawing issue which eliminates the toll grade battery supply.


Coin Station Test Line

A Coin Station Test Line Circuit SD-1C297-01 is available to assist the coin station repairperson in testing the capabilities of the coin telephone without the need for a test deskperson.  This circuit, which was introduced in 1971 was covered by EL 1388 (GL 71-07-150), can test either CF or DTF wired coin stations in all types of central offices.  When changing from CF to DTF operation there is an option change which must be made in the test circuit (remove option "S" on SD-1C297-01).

Coin Instruction Cards

The recommended format for coin instruction cards is covered in GL 73-11-069.  This letter covers the recommended format for 20 cent initial deposit rates at CF or DTF telephones and is adaptable to other rate situations.  The more standard the instruction cards are made, the more easily the customer can identify the services the coin telephone provides.

Coinless Call Completion

Implementation of DTF coin operation provides the coin telephone customer with the ability to reach the operator, directory assistance operator or emergency center (911) without the need for an initial coin deposit.  While this gives the customer the capability of making information or special toll calls (collect, credit card or third number billed) even without coins, it also increases the probability of other type of calls.

Permanent Signals

The introduction of DTF can result in a higher instance of permanent signals.  A receiver off-hook will result in a permanent signal.  With CF operation a coin deposit in addition to a receiver off-hook is required to get a call into the permanent signal conditions.

Coin Station Code Significance

Code      Housing Type    Mode of Operation                Dial Type

1A1       Box             Coin First Only                  Rotary
1A2       Box             Coin First Only                  Touch-Tone®

2A1       Panel           Coin First Only                  Rotary
2A2       Panel           Coin First Only                  Touch-Tone®

1C1       Box             Coin First or Dial Tone First    Rotary
1C2       Box             Coin First or Dial Tone First    Touch-Tone®

2C1       Panel           Coin First or Dial Tone First    Rotary
2C2       Panel           Coin First or Dial Tone First    Touch-Tone®

1D1       Box             Dial Tone First Only             Rotary
1D2       Box             Dial Tone First Only             Touch-Tone®

2D1       Panel           Dial Tone First Only             Rotary
2D2       Panel           Dial Tone First Only             Touch-Tone®

1E1       Box             Post Pay                         Rotary
1E3       Box             Post Pay                         None (manual)

More pay phone information in the upcoming GBPPR 'Zine issues.