Field Telephone, EE 8-A
From the Camp Crowder Central Signal Corps School Workbook

Testing the Telephone:

1. When no other telephone is available:

Test	By	Result
Generator	Shorting the line terminals with the TL-13's.	If the generator circuit is in good condition, the hand generator crank will turn hard when L1 and L2 are shorted, and easy when L1 and L2 are not shorted.
Transmitter and Receiver Circuits	First inserting the battery in the battery compartment and then pressing in and releasing the transmitter switch while blowing in the transmitter and listening in the receiver for a sidetone.	If the transmitter and receiver are in good condition, you should hear no sidetone when the switch is released; you should hear a sidetone when the switch is pressed.

2. When another telephone in good condition is available, connect the two telephones.

Test	By	Result
Hand Generator	Turning hand generator crank.	If the generator circuit is in good condition, the ringer on the other telephone should ring.
Transmitter Circuit	Inserting the batteries into the telephone and then pressing the transmitter switch and talking into it.	If the transmitter circuit is in good condition, the man on the other telephone should be able to hear you.
Receiver Circuit	Listening in the receiver while someone is talking into the transmitter of the other telephone.	If your receiver circuit is in good condition, you should be able to hear the man on the other telephone.
Ringer	Having the man on the other telephone turn his hand generator crank.	If your ringer is in good condition, your telephone should ring.