To serve more than 12 but fewer than 30 lines, stack the 12-line switchboards. Remove the operator's pack from the switchboard and install five line packs in the empty space. Place this modified switchboard on top of a normally equipped switchboard. Use two jumpers to connect the two switchboards. One jumper must be connected to the NA binding posts of both switchboards, and the other jumper must be connected to the GND binding posts of both switchboards. Be sure that the jumpers pass through the slot at the side of each switchboard. Only one set of batteries is required to serve both switchboard; remove the battery case from the one containing the 17 line packs (from which the operator's pack has been removed). The field telephones can then be connected. A maximum of 29 lines can be served with this arrangement as shown in figure 11-26.

RADIO AND TELEPHONE PROCEDURES

Even though your primary duties are those of a rifleman, machine gunner, or mortarman, you may be called upon to pick up a radio to pass some valuable information to one of the platoons or to the battalion headquarters.

The intent of this section is to provide enough knowledge of correct radio and telephone procedures so you can operate the voice radio equipment in a Seabee battalion.

The following terms are defined to give you a better understanding of the explanations in the following section:

1. TRANSMISSION: A communication sent by one station and intended for reception by another station or stations.

2. ANSWER: A transmission made by a station called in response to the call received.

3. CALL SIGN: A call sign is a word, or a combination of words, intended for transmission by voice means, and it identifies the command, unit, or authority of the radio station.

4. NET CALL SIGN: The collective call sign that represents all the radio stations operating together on a particular radio net.

5. NET CONTROL STATION: A radio station appointed by higher authority to direct and control the operation and flow of all traffic handled on the radio net.

6. PROWORD: A pronounceable word or phrase that has been assigned a meaning to speed up message handling on radio nets that use radio and telephone. A list of prowords and their meanings is presented later in this section.

7. ABBREVIATED PLAINDRESS MESSAGE: A message that has certain elements of the message heading omitted for speed of handling. Anyone or all of the following may be omitted: precedence, date, date-time group, and group count.

8. RECEIPT: A communication sent by the receiving operator indicating that the message or other transmission has been satisfactorily received.

9. ACKNOWLEDGMENT: A separate message originated by the addressee to inform the originator that his message has been received and is understood.