Introduction
The 177A test set is designed to monitor the voltage polarity and levels provided to the coin telephone set from any type of Central Office (CO), test desk, test console, test cabinet, line status verifier, or mechanized loop testing system.
The 177A test set Light Emitting Diodes (LED) respond to negative or postive potentials across the loop, or to either side of the loop to ground. A third wire is also provided with LEDs for tip to ground tests. Alternating Current (AC) and superimposed potentials can also be determined and identified. The 177A test set may be used for monitoring on an in-service basis without interfering with the circuit operation. It can also be used to determine trouble conditions when circuits are in the idle state. Foreign Electromotive Force (FEMF) trouble conditions are readily identified without fear of burning the trouble condition clear.
Listed are sample test procedures and the signaling threshold required for Dial Tone First (DTF) service. From this it can be determined the signaling application to be monitored. The test set can be connected at the station, central office terminal locations, or any location where tip, ring and ground can be accessed.
Signaling Threshold for Dial Tone First
Sample Test Procedures Using the 177A Test Set
Test Set Lead Connections
GREEN and RED from the 177A test set connecting cord to the TIP and RING of the line. YELLOW lead from the connecting cord to the central office or station GROUND.
Dial Tone First Mode (Local Call)
Local Overtime Call
Test set connected to a DTF line appearance in the central office or at the station.
| Step | Action | Verification |
|---|---|---|
| 1 | With handset on-hook. | No. 1 LED (-48 VDC) lights brightly, indicating battery and ground from the line equipment. |
| 2 | Go off-hook. | No. 1 LED (-48 VDC) goes dim, indicating battery and ground (dial tone) from the CO or test desk. No. 5 LED may light (dim) on loops equipped with Dial Long Line (DLL) or Signaling Range Extenders (SRE). |
| 3 | Deposit initial rate and dial local charge number. | No. 1 LED follows dial pulses. At completion of dialing, No. 6 LED (-48 VDC) lights momentarily, indicating initial rate ground test. |
| 4 | Call answered. | No. 1 LED (-48 VDC) now lit. |
Automatic 5 Cent Overtime
| Step | Action | Verification |
|---|---|---|
| 1 | At the end of 4-1/2 minutes. | No. 4 and 5 LEDs (+130 VDC) light and go dark, indicating a coin was collected. |
| 2 | Trip hopper trigger to simulate local overtime deposit. | |
| 3 | At the end of first 5 minutes. | No. 2 LED (+48 VDC) lights momentarily, indicating totalizer homing battery has been applied. No. 5 LED (+48 VDC) flashes, indicating coin present test. |
Dial "0" and Call (TSP, TSPS, Cord Board)
| Step | Action | Verification |
|---|---|---|
| 1 | With handset on-hook. | No. 1 LED (-48 VDC) lights bright. |
| 2 | Go off-hook. | |
| 3 | Dial "0" + (local charge number). | Just prior to operator answer, No. 3 and 6 LEDs flash, representing coin refund. |
| 4 | Operator answer. | No. 2 LED (+48 VDC) lights, indicating positive talking battery for totalizer homing. |
| 5 | Trip hopper trigger and request operator to collect. | No. 4 and 5 LEDs flash once, indicating +130 VDC coin collect pulse. |
continued...
| Step | Action | Verification |
|---|---|---|
| 6 | Request operator to ring back and hang up. | No. 1 and 2 LEDs glow following 20 cycle ringing supply, indicating ringing current applied. |
| 7 | Trip hopper trigger and request operator to refund. | No. 3 and 6 LEDs flash once, indicating -130 VDC coin refund pulse. |
Incoming Toll (Collect)
| Step | Action | Verification |
|---|---|---|
| 1 | Have operator initiate call to coin test station. | No. 1 or 2 LED lit prior to ringing. Both diodes are lit during ring. |
| 2 | Go off-hook. | No. 1 and 2 LEDs go dark. No. 2 LED lights, indicating +48 VDC talking battery on line. |
| 3 | Request operator to identify deposit. Deposit less than initial rate. | No. 2 LED remains lit, totalizer homes, operator can identify deposit. |
| 4 | Request operator to refund. | No. 2 LED goes dark, No. 3 and 6 LEDs flash, indicating -130 VDC coin refund pulse. No. 2 LED lights. |
| 5 | Trip hopper trigger and request operator to collect. | No. 2 LED goes dark, No. 4 and 5 LEDs flash, indicating +130 VDC coin collect pulse. |
| 6 | Request operator to disconnect circuit. | |
| 7 | Hang up. | No. 2 LED goes dark. No. 1 LED lights. |
Recycle
| Step | Action | Verification |
|---|---|---|
| 1 | At coin station, block coin relay armature (non-operational). | |
| 2 | Lift handset. | |
| 3 | Deposit initial rate and dial a local test number for audible ring (busy). | No. 1 LED lights, follows dial pulses. Audible heard. |
| 4 | Hang up. | No. 1 LED goes dark, No. 3 and 6 LEDs flash, indicating a -130 VDC coin refund pulse. No. 5 LED lights, indicating +48 VDC stuck coin test. No. 3 and 6 LEDs flash, indicating a second coin refund pulse. |
| 5 | Remove blocking tool. | No. 1 LED lights. |
| 6 | Go off-hook, then hang up. | No. 1 LED goes dark momentarily, No. 3 and 6 LEDs flash once, indicating a -130 VDC coin refund pulse. |